FIELD RESEARCH REPORT: NEW ZEALAND SEA LION MONITORING AT CAMPBELL ISLAND 2019 2020 - PREPARED BY: HELEN L. MCNUTT
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Field Research Report:
New Zealand Sea lion Monitoring at Campbell Island
2019 – 2020
Prepared by: Helen L. McNutt
Input from: Dahlia Foo, Nia Weinzweig
31 March 2020
1
Document Distribution List
Company/Organisation Name of Individual and Position Copy No.
DOC Kristopher Ramm, Mountains to Sea 1
DOC Katie Clemens-Seeley, Marine Species and Threats 2
DOC Amelie Auge, Mountains to Sea 3
Cawthron Institute Simon Childerhouse, Senior Research Scientist 4
DOC Ian Angus, Marine Species and Threats 5
Document Revision Record - DOC-6262035
Rev. Date Description Prepared Reviewed Approved
1.0 10/03/2020 Statistical Analysis/Data for Internal Review HLM SC
1.1 16/03/2020 First Draft Report for Internal Review HLM SC
1.2 17/03/2020 Second Draft Report for Team Review HLM DF, NW
1.3 22/03/2020 Final Draft Report for Internal Review HLM KCS, AA
1.4 27/03/2020 Final Report Submitted HLM IA IA
This report contains photos of deceased animals on pages 28 to 32 that may
disturb some readers.
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Field report NZSL Campbell Island 2019/20
Table of Contents
List of Figures ............................................................................................................................ 4
List of Tables ............................................................................................................................. 6
1. Executive Summary ............................................................................................................... 7
2. Introduction ............................................................................................................................ 8
3. Objectives .............................................................................................................................. 8
4. Methodology .......................................................................................................................... 9
4.1 Logistics ........................................................................................................................... 9
4.1.1 Summary of Key Dates: .......................................................................................... 12
4.2. NZSL Breeding Colonies ............................................................................................. 13
4.2.1 Davis Point Colony ................................................................................................. 13
4.2.2 Shoal Point Colony ................................................................................................. 14
4.2.3 Paradise Point East .................................................................................................. 14
4.3 Direct Counts ................................................................................................................. 15
4.3.1 Daily Pup Counts .................................................................................................... 15
4.3.2 Weekly Colony Counts ........................................................................................... 16
4.4 Flipper Tagging Pups ..................................................................................................... 16
4.5 Pup Production Estimates .............................................................................................. 17
4.5.1 Mark-recapture ........................................................................................................ 17
4.6 Pup Morphometrics ........................................................................................................ 17
4.7 Tag Re-sighting .............................................................................................................. 18
4.8 Pup Gross Post-mortems ................................................................................................ 18
4.9 Terrain Trap Mitigation ................................................................................................. 19
5. Results .................................................................................................................................. 19
5.1 Overall Environmental Conditions ................................................................................ 19
5.2 Direct Counts and Colony Movements .......................................................................... 19
5.2.1 Daily Live Pup Counts ............................................................................................ 19
5.2.2 Weekly Colony Counts ........................................................................................... 20
5.2.3 Challenges of Conducting Direct Counts ............................................................... 21
5.3 Flipper Tagging .............................................................................................................. 23
5.3.1 Flipper Tag Loss ..................................................................................................... 23
5.4 Pup Production Estimates .............................................................................................. 24
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Field report NZSL Campbell Island 2019/20
5.4.1 Pup Production at Paradise East ............................................................................. 26
5.5 Mark-Recapture Estimates ............................................................................................. 26
5.6 Pup Mortality ................................................................................................................. 27
5.6.1 Challenges of Accessing Dead Pups ....................................................................... 27
5.6.2 Overall Mortality Rates........................................................................................... 28
5.6.3 Gross Post Mortems ................................................................................................ 31
5.7 Pup Morphometrics ........................................................................................................ 34
5.8 Tag Re-sights ................................................................................................................. 36
5.9 Mitigation of Pup Mortality in Terrain Traps at Davis Point ........................................ 37
6. Discussion and Recommendations ...................................................................................... 39
7. References ............................................................................................................................ 42
8. Appendix A .......................................................................................................................... 43
List of Figures
Figure 1. Map of Campbell Island. ............................................................................................ 9
Figure 2 Davis Point research team. Left to right: Alex Pan, Lou McNutt (Team Lead) and
Dahlia Foo (McNutt, 2020)...................................................................................................... 10
Figure 3. Shoal Point research team. Left to right: Nia Weinzweig (Site Lead), Nathanial Scott
and Tamar Wells (Weinzweig, 2020). ..................................................................................... 11
Figure 4. Map of Davis Point colony indicating key site features, terrain traps, campsite, and
boat drop-off points................................................................................................................ 153
Figure 5. Map of Shoal/Paradise Points indicating the movement of the breeding colonies over
multiple years and the campsite ............................................................................................... 15
Figure 6. Daily live counts of New Zealand sea lion pups at Davis and Shoal Point colonies,
Campbell Island, 2019/20... ..................................................................................................... 20
Figure 7. Shoal Point colony at Campbell Island. The tall dense tussocks make it difficult to
obtain accurate NZSL counts (Weinzweig, 2020) .................................................................. 22
Figure 8. Shoal Point colony at Campbell Island. The colony breeding site was located atop
ridge on a steep sided narrow point (Weinzweig, 2020). ........................................................ 22
Figure 9. Slippery steep slopes and tidal areas made movement around the Shoal Point colony
to conduct counts challenging (Weinzweig, 2020). ................................................................. 23
Figure 10. Tag loss on NZSL pups at rock colony, Davis Point. Photos show how the skin at
the tag insertion area has stretched, facilitating tag loss (McNutt, 2020).. .............................. 24
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Field report NZSL Campbell Island 2019/20
Figure 11. Annual NZSL pup production, for years surveyed, at Davis and Shoal Points,
Campbell Island (McNutt, 2020).. ........................................................................................... 25
Figure 12. Researchers at Davis Point discuss how best to retrieve a deceased pup from the
colony, in the presence of a territorial male (Foo, 2020).. ....................................................... 28
Figure 13. Dead pups inaccessible in the centre of bog colony, Davis Point (McNutt, 2020)...
.................................................................................................................................................. 28
Figure 14. Mass mortality event at bog colony, Davis Point, after a bad weather event. Red
arrows indicate location of dead pups (McNutt, 2020)............................................................ 30
Figure 15. Daily (bars) and cumulative (lines) pup deaths at the Davis Point colony from 29
December 2019 – 24 January 2020 .......................................................................................... 30
Figure 16. A.Pan conducts a necropsy on a deceased NZSL pup at Davis Point (Foo, 2020).
.................................................................................................................................................. 31
Figure 17. Gross post-mortems were conducted on deceased NZSL pups to determine causes
of mortality. Mud in the oral cavity (Left) and in the stomach (Right) indicate drowning (Wells
& McNutt, 2020)...................................................................................................................... 32
Figure 18. Assessment of stomach contents from gross post-mortems on deceased NZSL pups,
at Davis Point ........................................................................................................................... 33
Figure 19. Assessment of stomach contents from gross post-mortems on deceased NZSL pups,
at ShoalPoint ............................................................................................................................ 33
Figure 20. Challenges when resighting tagged individuals included mud and faded tag
identification numbers (Foo, 2020).......................................................................................... 37
Figure 21. A pup trapped in a known terrain trap near bog colony, Davis Point (McNutt, 2020)..
.................................................................................................................................................. 38
Figure 22. A pup exits a rockpool at Davis Point colony. In storm events, pups would struggle
in the cold, wet conditions to exit the pools via the slippery rock slopes (McNutt, 2020)...... 39
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Field report NZSL Campbell Island 2019/20
List of Tables
Table 1. Summary of key dates NZSL research on Campbell Island during 2019/2020 field
season………………………………………………………………………………………...12
Table 2. Weekly colony counts of NZSL’s at Campbell Island 2019/20 .............................. 251
Table 3. Number of live pups double flipper tagged at Campbell Island NZSL colonies in the
2019/20 season ....................................................................................................................... 253
Table 4. Estimates of pup production and mortality for NZSLs at Campbell Island 2019/20..
.................................................................................................................................................. 25
Table 5. Mark recapture estimates for pup production at Davis Point, 2019/20. .................... 26
Table 6. Pup production and early mortality at Campbell Island, 2007-2020 ......................... 29
Table 7. Mean (± SE) pup weights recorded at Campbell Island NZSL colonies during field
seasons. Measurements for the Auckland Islands (Enderby and Dundas Island) in 2019/20 are
also included for comparison ................................................................................................... 35
Table 8. Mean (± SE) pup girths recorded at Campbell Island NZSL colonies during field
seasons. Measurements for the Auckland Islands (Enderby and Dundas Island) in 2019/20 are
also included for comparison ................................................................................................... 35
Table 9. Mean (± SE) pup lengths recorded at Campbell Island NZSL colonies during field
seasons. Measurements for the Auckland Islands (Enderby and Dundas Island) in 2019/20 are
also included for comparison ................................................................................................... 36
Table 10. Number of tag resights at each location by colour and sex. Breeding season in which
NZSLs were tagged as pups on Campbell Island is shown in brackets ................................... 37
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Field report NZSL Campbell Island 2019/20
1. Executive Summary
A survey of New Zealand sea lions (NZSL, Phocarctos hookeri) at Campbell Island (also
known as Motu Ihupuku) was undertaken during the 2019/20 breeding season. This survey
represented the third consecutive field research season undertaken as part of the 5-year NZSL
Threat Management Plan. The research team arrived on Campbell Island on 26th December
2019 and departed on 12th February 2020. The main aims of the work were to estimate total
pup production for the season and characterise early season pup mortality. The methodology
of the fieldwork followed that of previous surveys in 2017/18 and 2018/19 to ensure
comparability between years.
In summary:
• Shoal Point colony was in the same general breeding location as 2018/19.
• 223 were double flipper tagged on Campbell Island between 7 January 2020 and 16
January 2020 at Davis Point (n=152) and Shoal Point (n=71). No pups were tagged
outside of these locations.
• The overall male to female sex ratio of tagged pups on Campbell Island was 1.28 : 1.00
(males n=125; females n=98).
• Total estimated pup production for Campbell Island in 2019/20 was 595 comprising
448 pups from Davis Point, 139 pups from Shoal Point and an additional 8 pups found
outside these areas (Beeman Base 2; Paradise East 5; NW Bay 1)
• Davis Point pup production has declined slowly over the last three consecutive seasons.
• Overall, pup mortality was 81% for Campbell Island (i.e. 480 dead of 595 born).
• In comparison to the previous two seasons, each colony had the highest pup mortality
rates estimated up to 24 January (Davis Point 89%; Shoal Point 58%).
• Extreme wet and cold weather events early in the breeding season appeared to be the
primary contributing factor to the high pup mortality at Campbell Island.
• Mean estimates (±SE) for pup mass at Davis Point (female = 9.4 kg (0.2); male = 10.4
kg (0.3)) and Shoal Point (female = 9.2 kg (0.2); male = 10.3 kg (0.5)).
• At both Davis and Shoal Point colonies, both male and female pups were lighter than
all previous seasons.
• A total of 54 pups were necropsied, between 30 December 2019 and 16 January 2020,
of which 19 % pups had a blubber depth of 2 mm or less.
• No terrain trap mitigation was installed this season at Davis Point. Only two pups were
rescued by researchers, one from a bog and rockpool respectively.
• A total of 50 tag resights (i.e. full four code, alpha-numeric identification recorded) of
sea lions were collected. Most (90%) of resights were from Davis Point.
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Field report NZSL Campbell Island 2019/20
2. Introduction
New Zealand (NZ) sea lions (hereafter NZSL) are New Zealand’s only endemic pinniped
(Maloney et al. 2012). Currently classified as ‘nationally vulnerable’ the current population is
estimated at fewer than 12,000 individuals, with more than 98% of breeding occurring at a
small number of breeding sites at the Auckland Islands and Campbell Island (also known as
Mauka Huka and Motu Ihupuku, respectively) in the New Zealand subantarctic (Childerhouse
et al, 2015).
Campbell Island is the only significant breeding site outside of the Auckland Islands (Maloney
et al. 2012) and is comprised of two current breeding colonies; Davis Point and Shoal Point. In
2010, it was estimated to contribute approximately 27% of the total pup production for the
species (Maloney et al. 2012). Given its significance to the species, the Campbell Island sea
lion population has been studied consecutively for the past three summer seasons, as a
commitment through the New Zealand sea lion/Rāpoka Threat Management Plan.
The best index of population status for most pinniped species is pup production. Currently
Campbell Island experiences high pup mortality (e.g. 40-60%) during the first two months
post-partum (Foo and Weir, 2018), which is significantly higher than the usual observed pup
mortality at the Auckland Islands. Contributors to low pup survival in the subantarctic colonies,
include factors such as disease caused by the bacteria Klebsiella pneumoniae (Childerhouse et
al. 2014; Roe et al. 2014) starvation/exposure (associated with poor breeding habitat), trauma,
pups drowning or being trapped in natural terrain traps (Childerhouse et al. 2015). In 2018/19,
starvation/exposure (i.e. hypothermia) was the main source of pup mortality, primarily at Davis
Point (Foo and Weir, 2018).
A focus of the fieldwork this season was to estimate pup production at Campbell Island and
understand the causes of pup mortality. This research directly contributes to the improved
monitoring and management of NZSLs at Campbell Island.
3. Objectives
The aims of this project were to:
1. Estimate pup production at Davis Point and Shoal Point colonies for the 2019/20 season
2. Double flipper tag as many pups as possible at Davis and Shoal Point after 7 January
2020
3. Conduct mark-recapture estimates at Davis Point to trial the technique at Campbell
Island
4. Record daily sightings of tagged NZSL
5. Weekly counts of NZSL at the two colonies
6. Conduct gross post mortems (GPM’s) on a specified number of pups at each site (Davis
n=45; Shoal Point n=25) to investigate factors contributing to early pup mortality
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Field report NZSL Campbell Island 2019/20
7. Measure and weigh a cross-sectional sample of pups at both sites on specified dates;
and
8. Ensure comparability with previous surveys dates and methods to allow for direct
comparisons of data
4. Methodology
4.1 Logistics
Field work was undertaken on Campbell Island (53⁰S, 168⁰E), New Zealand from 26
December 2019 until 12 January 2020. Six researchers (forming two teams) were present on
the island, primarily based at the breeding colonies of Davis Point and Shoal Point in
Perseverance Harbour (see Figure 1; Childerhouse, 2015, p.8).
Figure 1. Map of Campbell Island
Note. Adapted from “New Zealand Sea lion Research at Campbell Island – Motu Ihupuku, 2014/2015”
Childerhouse, S., 2015, p.8.
The team of researchers undertaking the work during the 2019/20 field season were:
Davis Point - Lou McNutt (Team Lead), Alex Pan and Dahlia Foo (see Figure 2).
Shoal Point - Nia Weinzweig (Site Lead), Tamar Wells and Nathanial Scott (see Figure 3).
Each team consisted of a veterinarian (for undertaking necropsies) and a researcher who had
previously worked on the NZSL surveys at the colony, to provide site specific experience and
ensure consistency with previous surveys. All team members were current in their first aid
training, with the Team Lead holding additional Pre-Hospital Emergency Care (PHEC)
certification.
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Field report NZSL Campbell Island 2019/20
The vessel, Tranquil Image, transported the research team to Campbell Island. Researchers,
along with the supplies required for a 6-week field season (e.g. food, drinking water, tents, field
and camping equipment), were transported to their respective colonies. Temporary campsites
were then erected near the NZSL colonies at Shoal and Davis Point.
Upon arrival at Campbell Island, 3 days were spent by the research teams unloading supplies
at Beeman Base, setting up their campsites and gaining familiarity working around the colony.
Initially, research teams spent 10 days at their colonies, then regrouped at Beeman Base for 2-
3 days. Another 10 days followed at the colonies before the Shoal Team headed to Beeman
Base for 2 days’ rest. The Davis team remained at their colony during this 14-day period (see
Table 1) to continue data collection. Both research teams packed up their campsites on 24
January 2020, coinciding with the general breakup of the colonies, and made their way to
Beeman Base.
Researchers were at Beeman’s Base from 26 January to 11 February 2020. Extreme weather
conditions inhibited passage of the vessel Awesome to Campbell Island and delayed the
collection of researchers. A passing tourist vessel Ortelius collected the research team from
Campbell Island on 12 February 2020.
Figure 2. Davis Point research team. Left to right: Alex Pan, Lou McNutt (Team Lead) and Dahlia
Foo. (McNutt, 2020).
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Field report NZSL Campbell Island 2019/20Figure 3. Shoal Point research team. Left to right: Nia Weinzweig (Site Lead), Nathanial Scott
and Tamar Wells. (Weinzweig, 2020).
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Field report NZSL Campbell Island 2019/204.1.1 Summary of Key Dates:
Table 1. Summary of key dates NZSL research on Campbell Island during 2019/20 field season.
Date Activity
11 - 15 Nov Team Training, Wellington
11 - 13 Dec Pre-quarantine Invercargill
16 - 19 Dec Personal quarantine of team gear
23-Dec Depart for Campbell abroad 'Tranquil Image'
26-Dec Arrive Campbell Island. Davis Team disembark and set up campsite
27-Dec Shoal Team disembark and set up campsite
29-Dec Daily pup counts and Gross Post mortems begin
29-Dec Initial NZSL colony count (Davis)
3-Jan Weekly NZSL colony count (Shoal and Davis)
4 - 6 Jan Teams meet at Beeman Base
7-Jan Pup flipper tagging starts
10-Jan Weekly NZSL colony count (Shoal and Davis)
13 - 14 Jan Pup Weigh Days (Shoal and Davis)
15 - 16 Jan Pup Mark Recapture at Davis Point Colony
15-Jan Shoal Team visit Paradise East
17-Jan Weekly NZSL colony count (Shoal and Davis)
18 - 20 Jan Shoal Team rests at Beeman’s Base
23 - 24 Jan Final NZSL colony count
24-Jan Daily Pup counts end. Pack up campsites. Shoal Team hikes to Beeman Base
25-Jan Davis Team hikes to Beeman Base
26 Jan - 12 Feb Teams at Beeman Base waiting collection. On standby due to poor weather conditions
12-Feb Depart Campbell Island abroad tourist vessel 'Ortelius'
15-Feb Arrive in Bluff
16-Feb Team departs for home
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Field report NZSL Campbell Island 2019/204.2. NZSL Breeding Colonies
The only two breeding colonies for NZSL on Campbell Island are at Shoal Point and Davis
Point. Boundaries of NZSL breeding colonies were defined as “areas where groups of pups
are born” (Childerhouse, 2019, personal correspondence). Upon arrival, researchers recorded
colony boundaries using a handheld GPS unit, thereby defining the initial area within which
NZSL counts were undertaken. Later in the season, as the pups became more mobile and began
to explore further from the central colony area, the count area was broadened to accommodate
this. Counts however, did not exceed the main colony area as shown in Figure 4 (Foo and Weir,
2018, p.11).
4.2.1 Davis Point Colony
Davis Point comprises of two sub-colonies; Bog and Rock colony respectively (see Figure 4;
Foo and Weir, 2018, p.11). The sub-colonies adjoin each other and their boundaries have
remained relatively unchanged (Foo and Weir, 2018) from initial censuses in 1998. Detailed
descriptions of the Davis Point colony can be found in a previous report (Childerhouse et al.
2015). The defining feature between the two sub-colonies is the differing substrate and
presence of vegetation. Bog colony is predominately a peat platform bordered by large clumps
of tussock. It is characterized by slippery, soft mud and deep boggy holes, in wet conditions.
These boggy areas act as terrain traps and are a potential threat to NZSL pups (Childerhouse et
al. 2015; Foo and Weir, 2018; Lea et al. 2018). High sided and slippery, pups that fall into
these mud holes can struggle to climb out, often succumbing to exhaustion and drowning in
mud. Rock colony is an unvegetated, broad rock platform with several pools, of varying
dimensions (Foo and Weir, 2018). Both sites are extremely exposed and offer very limited
shelter to pups in wet, windy conditions.
Figure 4. Map of Davis Point colony indicating key site features; terrain traps, campsite, boat
drop-off point and location of fish bins, containing food supplies.
Note. Reprinted from “2018/19 Campbell Island (Motu Ihupuku) New Zealand Sea lion Research Trip Report,
Foo and Weir, 2018, p.11.
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Field report NZSL Campbell Island 2019/204.2.2 Shoal Point Colony
The breeding colony at Shoal Point is relatively new (e.g. since 2018) and prior to this a group
of NZSL have bred in different locations along the southern shoreline of Perseverance Harbour
since approximately 2008 (see Figure 5; Foo and Weir. 2018, p.12). Initial surveys undertaken
during 2014/15 reported two sub-colonies present, east of Shoal Point, along this southern side
of Perseverance Harbour; Paradise Point East and Paradise Point West (Childerhouse et al.
2015). Surveys in 2017/18 indicated the Paradise Point West sub-colony had continued to move
westward, establishing a breeding site at Shoal Point. This resulted in change of name for this
colony (Foo and Weir, 2018). The Shoal Point colony shifted westward again in 2018/19 (Foo
and Weir, 2018) but has remained in this general location for the 2019/20 breeding season.
Observations of heightened NZSL activity were noted above the campsite this season (Scott,
2019, personal communication). In addition, sections along the coastline, either side of the
main Shoal Point breeding site, showed evidence of sealion activity (i.e. flattened vegetation
and muddy trampled ground) (Weinzweig, 2019, personal communication). The Paradise Point
East colony has dispersed and is no longer active with the presumption that the NZSLs from
that colony have moved into Shoal Point.
Shoal Point colony is situated on a prominent point and boxed in on three sides. Bounded on
its eastern and western sides by steep rocky cliffs and bordered to the south by a steep forested
slope (Foo and Weir, 2018). Access around the point, via the foreshore, is tidal (Weinzweig,
2020, personal correspondence). Consequently, the bulk of the breeding colony occupies a
small plateau atop the narrow steep sided spur. The area is heavily vegetated with large, dense,
tussocks (Weinzweig, 2020, personal correspondence).
4.2.3 Paradise Point East
One off surveys of Paradise Point East continue to be conducted each season to report presence
of NZSL activity and breeding colonies. Researchers visited the last known Paradise East
colony location (52.558⁰S, 168.201⁰E) on 15 January 2020.
14
Field report NZSL Campbell Island 2019/20Figure 5. Map of Shoal/Paradise Points indicating the campsite and movement of the breeding
colonies over multiple years.
Note: Reprinted from “2018/19 Campbell Island (Motu Ihupuku) New Zealand Sea lion Research Trip Report,
Foo and Weir, 2018, p.12.
4.3 Direct Counts
4.3.1 Daily Pup Counts
The number of live and dead pups were counted every morning, unless field work was put on
hold due to rest days or unfavourable weather conditions. Counts were typically conducted by
walking around the periphery of the colony and recording the number of individuals using a
tally counter. Later in the season, when bull NZSL were less aggressive and it was safe to do
so, counts were also conducted by walking through the Davis Point colony.
At Davis Point three researchers completed three individual counts each, per day. Numbers for
live and dead pups were then compared against those of colleagues. If the counts differed by
more than 10% another count was conducted, until numbers fell within this agreed range.
Pup counts at Shoal Point are more difficult and time-consuming due to terrain and vegetation
limiting visibility of NZSLs, as a result, two researchers each undertook a single count of live
pups, per day.
Each day, any freshly dead pups were counted and notes on the location recorded, at both sites.
Whenever possible, dead pups were removed from the main colony area and/or marked with
brightly coloured spray paint (FIL Tell Tail, Bay of Plenty, NZ). Dead pups removed from the
colony were piled together, away from the core breeding site, in an area not commonly
frequented by live pups. Thus, enabling researchers to keep track of newly dead animals and
prevent duplication in dead counts.
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Field report NZSL Campbell Island 2019/204.3.2 Weekly Colony Counts
Counts of all adult female, adult male and sub-adult male NZSLs, within the defined colony
boundary, were undertaken weekly at both sites, from 3 January 2020. Direct counts were
typically undertaken in the mornings (between 9am -11am). The manner in which counts could
be safely conducted was determined by the presence and location of aggressive territorial male
NZSLs and differed between sites and through the season.
At Davis Point, counts of bog colony were obtained from an elevated position which provided
an unobstructed view of the whole colony. Counts of rock colony were achieved by walking
around the periphery of the colony. The colony was sectioned into three divisions for counts.
Researchers counted the same section of the colony three times each, before moving on to
count the next section. A tally counter was used and all counts had to be ±10 % of each other,
or they were redone until this was achieved.
Direct counts at Shoal Point were more challenging due to the terrain, which is densely covered
in tall tussock, thereby limiting visibility of the colony and the location of peripheral males
(Weinzweig, 2020, personal correspondence). The colony was sectioned into seven areas. For
each section, a single direct count was undertaken simultaneously, whenever possible by each
of the research team. Counts were obtained by climbing atop tall tussocks, which provided a
safe vantage point.
4.4 Flipper Tagging Pups
Double flipper tagging pups is a method used for long-term population monitoring, as it
provides a pool of known age individuals for the estimation of survival, recruitment and
reproductive rate parameters (Chilvers, 2011).
Flipper tagging was conducted at Davis and Shoal Point colonies from 7 January 2020, when
pups were deemed to be of a significant age and mass to safely tag. The objective was to
double flipper tag as many live pups as possible at each location, with the ideal result being
all live pups tagged.
A description of the method used for tagging NZSL pups is outlined in the DOC NZSL and
Fur Seal Pup Tagging Standard Operational Procedures (SOP). Orange, coffin shaped, tags,
were used for 2019/20 Campbell Island season, at both colonies. Pups were tagged on both
flippers with matching identification tags (Superflexitag®, Dalton ID systems, Oxon, UK).
Each individual was tagged with a unique alpha-numeric identification code.
Prior to tagging, flippers were wiped with a rag to remove excess mud. Flipper tags were
inserted with the male pin facing outwards, to prevent abrasion against the body (i.e. the male
pin was inserted from underside the flipper). The puncture site (above and below the flipper)
was then sprayed with diluted Betadine solution, to reduce the risk of localised infection. The
sex of each pup was recorded, along with its unique tag code.
16
Field report NZSL Campbell Island 2019/204.5 Pup Production Estimates
Total pup production, for the 2019/20 season was calculated by adding the total number of
tagged live pups, untagged live pups and untagged dead pups, recorded at each colony.
Opportunistic sightings of untagged pups elsewhere on the island, away from the colonial
breeding sites, were also recorded. On 15 January 2020, Shoal Point researchers undertook a
survey to the last known breeding location at Paradise East (52.558⁰S, 168.201⁰E) to
investigate the presence of pup production at this site.
4.5.1 Mark-recapture
Mark-recapture method is commonly used to estimate population size, when it is impractical
to count every individual. This standard technique has been used at both Sandy Bay and Dundas
Island in the Auckland Islands for more than 25 years and is considered the most effective and
accurate way to estimate live pup numbers at colonies, where access to all pups is challenging
(Dodge, 2019).
A Mark-recapture was performed at Davis Point colony only as part of a pilot study for the use
of the technique at Campbell Island. On 15 January twenty-six live pups were marked by gluing
(Loctite®, Henkel Corp, USA) flexible round, white, PVC caps to their heads. Caps were put
out amongst pups in an approximate ratio of 1 cap for every 2-3 pups, across the whole area
where pups were present. Thus, a total of 11 caps and 15 caps were put out in bog and rock
sub-colonies respectively. Pups were allowed to reintegrate and mix back into the colony over
the following 24 hours. On 16 January, a recapture census was undertaken. Nine mark-
recapture counts were undertaken by three different people. Each researcher, with two tally
counters in hand, took turns to walk through the colony, recording the number of marked and
un-marked pups as they went. Pups were only recorded if 100% of the head could be seen were
included in the counts, to minimise the risk associated with undercounting unmarked pups
(Chilvers, 2012). A route, covering as much of the colony area as possible, was agreed upon
by researchers. Each walked a similar path through the colony and were sent through at
intervals of two minutes apart, to avoid disturbing the others count. Prior to the recapture, three
direct counts of dead pups were undertaken by the whole three-person team working together
and any capped pups that died overnight were removed from the total number of caps in
calculations. Additionally, any caps that were seen on the ground (e.g. had fallen off overnight)
were also removed.
The results of the mark-recapture were used to calculate live pup numbers, using a modified
Lincoln-Petersen formula for small sample sizes (Chilvers, 2012).
4.6 Pup Morphometrics
On 13 -14 January a random sample of 100 live NZSL pups (up to a maximum of 50 females
and 50 males) were caught and measured at Davis and Shoal Point. Sampling dates remained
consistent with previous seasons to allow comparison of data.
17
Field report NZSL Campbell Island 2019/20The methodology is outlined in further detail in the DOC NZSL and Fur Seal Pup Tagging
SOP, briefly it is as follows:
A canvas weigh bag was placed on hanging scales (Salter, Victoria, Australia) and zeroed. One
pup was caught, sexed, then placed in the canvas weigh bag. Weights were taken to the nearest
100g. Pups were removed from the weigh bag, placed on a measuring board or on the ground
and restrained by a researcher. Straight line measurements of standard length, from nose to tip
of tail (without following the curvature of the pup’s body) were recorded. Axillary girth
measurements were taken using a seamstress tape, placed firmly behind the fore flippers. Girth
measurements were recorded on the pups’ exhale. The flipper tag was recorded and the pup
was marked with a small dot on its back, with brightly coloured spray paint, before being
returned to the colony.
Prior to the next pup capture, the scales were re-zeroed with the canvas bag (to account for any
change in bag weight associated with the damp, muddy conditions).
4.7 Tag Re-sighting
Re-sighting of tagged subadult and adult NZSLs was done opportunistically, during daily
morning counts. The identification numbers of tagged animals were read either directly from
the flipper tag or by photographing the tag with a telephoto lens, then zooming in to read the
number from the camera screen. The animal’s sex, location, and tag’s colour, shape,
identification number and side were recorded.
4.8 Pup Gross Post-mortems
A maximum sample size of 45 and 25 opportunistic Gross post-mortems (GPM) were approved
after consultation with Ngāi Tahu for the project at Davis and Shoal Points, respectively.
To determine causes of early pup mortality, a range of health markers including the following
were assessed during necropsies; blubber depth, presence of milk in stomach, ulceration
severity on flippers, presence of mud in trachea, presence of pus in joints, presence of trauma
and presence of fluid in lungs. These were details in addition to normal GPM data recording.
Cross-sectional body measurements were recorded (weight, length and girth) along with sex
and notes on body condition and carcass flensing. No histological samples were taken.
The GPS location of every pup necropsied was recorded along with notes on substrate and
presence in relation to terrain traps (rockpools or bogs).
Based on the 2017/18 season observations, pup mortality is generally higher earlier in the
season (within the first week of January) and tends to taper off as the season progresses (Foo
and Scott, 2019, personal communication). Therefore, the aim for this season was to conduct
the bulk of pup necropsies during the first few weeks at the colony. This would cover sampling
during the period of highest pup mortality.
Selection of carcasses to necropsy were based on their freshness and ease of access. Whenever
possible fresh, less than day old carcasses were necropsied. Due to the presence of territorial
18
Field report NZSL Campbell Island 2019/20males and aggressive female NZSLs, at the start of the season, often only the dead pups located
near colony edges could be sampled.
4.9 Terrain Trap Mitigation
Historically, high mortality rates associated with NZSL pups drowning in muddy holes
(Childerhouse et al. 2016), has occurred at Davis Point (Lea et al. 2018). Placement of
mitigation equipment within these terrain traps has proven successful in reducing pup mortality
rates (Foo and Weir, 2018). Heavy duty hessian sacks were available this season, for
mitigation, as required. The hessian sacks are multi-purpose; they can be filled with dirt and
rocks and placed either in shallow bogs to help pups exit or along the cliff edge to act as a
barrier for pups (Foo and Weir, 2018).
5. Results
5.1 Overall Environmental Conditions
Campbell Island experienced extreme gale force winds this season. In one extreme weather
event, water spouts were observed crossing the harbour at the head of Perserverance, off Shoal
Point. Daytime temperatures typically hovered around 7-9°C and dropped at night. Days were
often overcast and daily rain squalls were the norm. Prevailing winds were typically from a
westerly direction.
The terrain and local climatic conditions at the two breeding colonies are different and, as a
result, each site experiences differences in early pup mortality rates. Shoal Point, located
toward the head of Perseverance Harbour, is densely vegetated unlike Davis Point which has
open mud or rock platforms. Furthermore, the location of Davis Point, at the eastern harbour
entrance means it is exposed (Foo and Weir, 2018) and offers NZSLs little shelter in prevailing
westerly winds and driving rain.
5.2 Direct Counts and Colony Movements
Direct daily counts of live and dead pups and weekly counts of adult females, adult and sub-
adult males were made at Davis and Shoal Point from 29 December 2019 until 24 January
2020.
5.2.1 Daily Live Pup Counts
The start of the pupping season at Campbell Island was not witnessed by the researchers. Teams
arrived on 29 December and by this time pupping was well underway at the colonies. At Davis
Point female NZSLs were frequently observed pupping up to 10 January, however, after this
date the number of newly born pups witnessed daily in the colony decreased.
19
Field report NZSL Campbell Island 2019/20Figure 6 provides a visual representation of the daily live pup counts obtained at Davis and
Shoal Point colonies over the 2019/20 season. A downward trend in daily live pup numbers at
the colonies was observed as the season progressed. This can be explained by the high pup
mortality rates, during inclement weather events, early in the season and later in the season
pups dispersing away from the main colony, up into the Dracophyllum forest.
Daily live pup counts at Campbell Island
350
300
Number of live pups
250
200
150
100
50
0
1 January 2020
2 January 2020
3 January 2020
4 January 2020
5 January 2020
6 January 2020
7 January 2020
8 January 2020
9 January 2020
23 January 2020
29 December 2019
30 December 2019
31 December 2019
10 January 2020
11 January 2020
12 January 2020
13 January 2020
14 January 2020
15 January 2020
16 January 2020
17 January 2020
18 January 2020
19 January 2020
20 January 2020
21 January 2020
22 January 2020
24 January 2020
Date
Davis Point Shoal Point Davis + Shoal Point
Figure 6. Daily live counts of New Zealand sea lion pups in the surveyed areas at Davis and Shoal
Point colonies, Campbell Island, 2019/20.
Gaps in the data series, as shown in Figure 6, occur when the teams were resting at Beeman
base, undertaking surveys at Paradise East or on one occasion during an extreme weather event
when Shoal team researchers felt it unsafe to conduct fieldwork at the colony (Weinzweig,
2019, personal communication).
5.2.2 Weekly Colony Counts
As expected NZSL’s numbers at the coastal colonies, were highest early in the breeding season,
when breeding females congregate, forming harems attended by a dominant male NZSL.
During this time other male NZSLs were frequently witnessed around the periphery of the
colony, often challenging the dominant territorial male. As the breeding season progressed and
pups became more mobile, female NZSLs, at both sites, gradually occupied more inland areas,
bringing their pups higher up the ridgeline. A dramatic decrease in NZSL present at the colony
was observed after 17 January. As the breeding season tapered off, the harems disbanded and
the number of dominant males witnessed in the colonies decreased. By the 24 January most
had dispersed, with only a few individuals remaining (see Table 2). Counts were stopped after
20
Field report NZSL Campbell Island 2019/20the pups had dispersed up the ridgeline into the Dracophyllum forest, due to the difficulty in
trying to locate them.
Table 2. Weekly colony counts of NZSL’s at Campbell Island 2019/20.
5.2.3 Challenges of Conducting Direct Counts
Fewer direct counts were undertaken by the Shoal Point research team (Weinzweig, 2019,
personal communication) due to the following factors:
• poor visibility of animals (high dense vegetation and a lack of vantage points);
• colony location on a narrow point (tides and steep sided slopes; Figure 8 and 9); and
• aggressive territorial males
Researchers had limited options on where access could be safely gained, in order to navigate
around the colony periphery during direct counts. The poor visibility due to high vegetation
(Figure 7), required one researcher to be constantly standing guard watching for any
approaching NZSLs, whilst the other two researchers conducted daily pup counts. This was
particularly important during the start of the season when researchers were still becoming
familiar with working around the colony (Weinzweig, 2019, personal communication).
Weather patterns were also noted to influence the behaviour of NZSLs within the colony and
therefore influence what fieldwork could be safely undertaken. At both sites, NZSLs exhibited
heightened levels of activity and aggressive behaviour on bad weather days. This combined
with the challenging terrain experienced underfoot (uneven, boggy and very slippery) meant it
was difficult to make a quick exit from the colony should the need arise.
The combination of these factors, and the safety and comfort level of the researchers in working
in close proximity to territorial males, dictated what fieldwork that could be carried out on a
daily basis.
The Shoal Point Team Leader noted, during daily surveys, that the longer time spent trying to
conduct counts of the colony, the more territorial the males became. As a result, due to concerns
21
Field report NZSL Campbell Island 2019/20over the team safety, counts were limited to a single count each. Low direct counts from Shoal
Point, therefore, may be an under-estimation due to these logistical and safety concerns.
Figure 7. Shoal Point colony at Campbell Island. The tall dense tussocks make it difficult to obtain
accurate NZSL (especially pup) counts (Weinzweig, 2020).
Figure 8. Shoal Point colony at Campbell Island. The colony breeding site was located atop
ridge on a steep sided narrow point (Weinzweig, 2020).
22
Field report NZSL Campbell Island 2019/20Figure 9. Slippery steep slopes and tidal areas made movement around the Shoal Point colony to
conduct counts challenging (Weinzweig, 2020).
5.3 Flipper Tagging
Two hundred and twenty-three live pups were tagged, with identical numbers in both flippers,
between 7 - 24 January (see Table 3). Flipper tags were orange, coffin-shaped, Dalton
Superflexi tags with an alpha numeric code (e.g. T0AH). No pups were microchipped this
season as per the work plan given the difficulties in previous years and the limited resighting
effort. The overall male to female sex ratio of tagged pups was 1.28 : 1.00 (males n=125,
females n=98).
Table 3. Number of live pups double flipper tagged at Campbell Island NZSL colonies in the
2019/20 season.
5.3.1 Flipper Tag Loss
Post-tagging observations of pups in rock colony at Davis Point observed 5 individuals where
the skin of the flipper had stretched around the area the tag pin was inserted (see Figure 10).
This was not observed in the pups at bog colony.
23
Field report NZSL Campbell Island 2019/20One lost flipper tag (XH9V) was retrieved from Bog colony. Checks of the unique
identification number indicated it was from a female pup tagged at Davis Point this season.
Figure 10. Tag loss on NZSL pups at rock colony, Davis Point. Photos show how the skin at the
tag insertion area has stretched, facilitating tag loss (McNutt, 2020).
5.4 Pup Production Estimates
Estimates of pup production and mortality are shown in Table 4. The key features are:
• The overall pup mortality was 81% for Campbell Island (i.e. 480 dead of 595 born).
• In comparison to the past two seasons, each colony had the lowest recorded pup
production (Davis Point n=448; Shoal Point n=139) and highest proportion of pup
deaths estimated up to 24 January (Davis Point 89%; Shoal Point 58%).
• Five pups were observed but not tagged at Paradise East on 15 January.
• Two pups were observed near Beeman Base but not tagged on 25 and 27 January.
• One pup was observed but not tagged during a hike to Norwest Bay (52.556⁰S,
168.088⁰E) on 28 January.
24
Field report NZSL Campbell Island 2019/20Table 4. Estimates of pup production and mortality for NZSLs at Campbell Island 2019/20.
A visual representation of annual pup production, is shown in Figure 11. A decline in pup
production numbers is recorded at Davis Point over the last three consecutive seasons. Overall
pup production, at the main breeding sites (Davis and Shoal Point) on Campbell Island, has
declined since the 2018/19 season, however this may be partly due to difficulties in obtaining
accurate pup counts, particularly at Shoal Point.
NZSL Pup Production at Campbell Island
750
700
650
600
550
Annual pup production
500
450
400
350
300
250
200
150
100
50
0
2007/2008 2009/2010 2014/2015 2017/2018 2018/2019 2019/2020
Year
Davis Point Shoal Point Davis + Shoal Points
Figure 11. Annual NZSL pup production, for years surveyed, at Davis and Shoal Points,
Campbell Island (McNutt, 2020).
25
Field report NZSL Campbell Island 2019/205.4.1 Pup Production at Paradise East
Visitation on 15 January to the last recorded breeding location at Paradise East (52.558⁰S,
168.201⁰E) from the 2018/19 field season, confirmed that NZSLs still utilise this location.
Evidence of heightened NZSL activity earlier in the season was prevalent as noted by the
flattened vegetation. Shoal Point Team Lead estimates there may have been as many as ten
harems in this area at the start of the season. This estimate was based on observations of the
size of the area flattened at Paradise Point East, then compared with the social spacing of
harems observed at Shoal Point (Weinzweig, 2020, personal communication). However, on
the date the researcher’s visited the site, the NZSLs had already begun to disperse up into the
forest. One harem comprising of five pups, one territorial male, two adult females and one
peripheral male were observed on the lower forest edge (Weinzweig, 2020, personal
communication). Pups were unable to be accessed and flipper tagged due to the aggressive
nature of the males.
5.5 Mark-Recapture Estimates
Twenty-six mark-recapture caps were put out on pups on 15 January at Davis Point. Of the
twenty-six pups capped on 15 January two capped pups were found dead, one in each of the
sub-colonies (i.e. 1 from bog and 1 from rock) prior to starting the mark-recapture counts on
16 January. The number of marked pups was, therefore, considered to be twenty-four for the
purposes of the mark-recapture estimation. Appendix A shows the mark-recapture counts
obtained in the field at Davis Point.
Estimates of live pup number at Davis Point were completed successfully (Appendix A). Nine
mark-recapture counts were undertaken by three different people. Prior to recapture counts,
three direct counts of dead and live pups were undertaken by the whole three-person team
working together. The mark-recapture estimate for live pups at Davis Point colony on 16
January was 53 (see Table 5).
Table 5. Mark recapture estimates for live pup number at Davis Point on 16 January,
2019/20.
1
Start and end times shown were for the entire duration it took to conduct direct counts and mark-recapture
counts at both Bog and Rock colonies at Davis Point.
Mark-recapture (M-R) was undertaken as pilot study to trial an alternative method for obtaining
live pup number estimates. Comparability, with the mean direct live pup count for 16 January,
at Davis Point, highlights it was successful (see Table 5). The M-R method, utilises the ratio
26
Field report NZSL Campbell Island 2019/20of marked to unmarked animals and is particularly useful in challenging environments (i.e.
dense vegetation, limited visibility, aggressive NZSLs) where it is difficult to obtain accurate
direct counts of all pups. An additional benefit of a M-R method for estimating pup production,
is that it is relatively quick to conduct. It can be completed over two days, and would allow
teams to focus their time on other tasks than daily live pup counts.
5.6 Pup Mortality
Researchers monitored pup mortality daily at Davis Point and Shoal Point for the duration of
their time present at the colonies and conducted necropsies on a sample of pups at each colony.
5.6.1 Challenges of Accessing Dead Pups
Early in the season highly territorial (i.e. aggressive) males prevented researchers from safely
accessing areas of Shoal and Davis Point colonies (see Figure 12), making it difficult to conduct
accurate dead pup counts. As a result, researchers were restricted to obtaining dead pup counts
from wherever a vantage point of the colony could be obtained. Whilst, this offered a safe
platform to conduct counts, at Shoal Point the terrain posed additional constraints, as tall
tussocks and steep sided cliffs limited the visibility to these areas of the colony.
With the majority of dead pups initially located in the central sector of the colonies researchers
were unable to retrieve or mark all individuals with spray paint during daily counts (see Figure
13). This made distinguishing a newly deceased pup from a day old, previously counted one,
partly subjective. Whilst discussion was undertaken between researchers within teams to agree
on which were new vs previously counted dead pups, it is important to note that where pup
mortality is estimated, there may be some slight duplication in daily numbers.
In addition, at bog colony, dead pups would be trampled into the mud by territorial bull NZSLs.
This imposed the complication, in that deceased pups could be difficult to distinguish when
buried in deep mud or be mistaken for a dirt mound. This consideration is important in that
despite best efforts to obtain accurate counts there is the possibility of missed dead pups,
particularly on days of mass mortality.
As the season progressed, obtaining accurate direct counts was easier, as NZSLs became less
aggressive and more accustomed to the presence of researchers. This facilitated better access
into the colony, whereby dead pups could be removed or marked.
27
Field report NZSL Campbell Island 2019/20Figure 12. Researchers at Davis Point discuss how best to retrieve a deceased pup from the colony,
in the presence of a territorial male (Foo, 2020).
Figure 13. Dead pups inaccessible in the centre of bog colony, Davis Point (McNutt, 2020).
5.6.2 Overall Mortality Rates
Pup mortality is presented in Table 6 (Foo and Weir. 2018, p. 21) with an overall level of 81%
by 24 January across both colonies; the highest recorded mortality rate since 2007. Compared
to previous research trips, with similar survey timings, pup mortality at Davis (89%) was
significantly higher. Lower mortality rates at Shoal Point (56%), in comparison to Davis Point,
continue to indicate that it is the more suitable pupping location.
28
Field report NZSL Campbell Island 2019/20Table 6. Pup production and early mortality at Davis and Shoal Point, Campbell Island,
2007-2020.
Note: Adapted from “2018/19 Campbell Island (Motu Ihupuku) New Zealand Sea lion Research Trip Report, Foo
and Weir. 2018, p. 21. Records of pup production at other locations on Campbell Island, outside of the main
breeding sites of Davis Point, Shoal Point and Paradise Point are not included here.
The exact reasons for the large difference in mortality rates between the colonies is unclear,
but is likely related to local environmental factors including; substrate, weather conditions,
shelter, presence of rock pools and bog holes.
Unlike the breeding site at Shoal Point, which is drier and more sheltered, the Davis Point
colonies are exposed. In wet conditions the site at bog colony transforms from a firm dry pan,
into quagmire. Natural depressions in the terrain quickly become deep boggy holes that trap
pups.
During inclement weather, pups were frequently observed shivering in the cold, wet muddy
conditions. Often huddling together in attempt to find shelter or laying on the bodies of other
deceased pups, thereby raising themselves out of the muddy conditions. It was not uncommon
for these pups to then be found dead in the same location the following day.
Researchers also noted behavioural changes within the colony during these poor weather
events. Male NZSLs exhibited heighted levels of aggression and activity and were more
frequently observed challenging and engaging in fights with neighbouring males. Pups
suffering from exposure (i.e. hypothermia) were at greater risk of being trampled by charging
males, as they are often too weak to move quickly out of the way.
Personal observations from researchers at Davis Point noted that mass mortalities (Figure 14)
of pups occurred during or after large storm events and periods of poor weather. One such
29
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