Effects of delayed dispersers on pup lifetime fitness in the red wolf, Canis rufus - Midwest Wolf Stewards Meeting April 22, 2010 Amanda Sparkman ...
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Effects of delayed
dispersers on pup
lifetime fitness in the
red wolf, Canis rufus
Midwest Wolf Stewards Meeting
April 22, 2010
~
Amanda Sparkman
Post-Doctoral Researcher
Trent University
Gregory Koch
The Red Wolf (Canis rufus) •Once distributed across the southeastern U.S. •1980: Declared extinct in the wild •1973: Endangered Species Act; captive breeding program established •1987: Reintroduction into Alligator River National Wildlife Refuge, NC •1987-2007: 463 wolves fitted with VHF collars
Cooperative Breeding – Present in ~3% mammals – Especially prevalent in rodents, mongooses, primates, and canids – Generally family groups with offspring with delayed dispersal
Delayed Dispersal
BENEFITS
Delayed dispersers
Group living
Increased survivorship
“Parenting” experience USFWS
Access to mates
Inclusive fitness COSTS
Delayed dispersers
Juveniles Delayed age at first reproduction
Group living Juveniles
Increased mass/size Competition with older siblings
Increased survivorship
Earlier age at first breeding
Increased reproductive probability
Questions
1. Do red wolves that
delay dispersal “help”?
• helping behavior
widespread in Canis sp.
• den‐site attendance
documented in red wolf
• may be resource‐
dependent
2. Are there long‐term
fitness benefits for pups
Gregory Koch
with helpers?
Delaying Dispersal
Majority of breeding red wolf packs composed of family members
– Few breed in natal pack (7/79)
– Earliest dispersal: 6 months
– 35% disperse at 0, 46% at 1, 18% at 2+
Gregory Koch
1. Do red wolves that delay dispersal “help”? Testing for effects of helper presence on mass/size • Pup mass: 6-8 months, controlled for age • Adult mass: 18+ months • Size measurements: PCA of ear, tail, hindfoot, and body length
Red Wolf Population Growth
140
Population Population
120 Growth I Growth II
100
Annual Wolf Count
Population
80 Saturation
60
40
20
0
1990 1992 1994 1996 1998 2000 2002 2004 2006
Year
U.S. Fish & Wildlife Service 2007PUPS ADULTS
4 A 29 B Females
3 Males
Pup mass (residuals from age)
27
2
Population 1 25
Adult mass (kg)
0
Growing 23
-1
-2 21
-3
N = 23 19 N = 46
-4
P = 0.007 P = 0.096*
-5 17
Helpers Absent Helpers Present Helpers Absent Helpers Present
* Significant for adult size
4
C 29 D
3
Pup mass (residuals from age)
2 27
1
Adult mass (kg)
25
Population 0
23
-1
Saturated
-2 21
-3
N = 77 19 N =36
-4
Sex*helpers P = 0.0848* P = 0.0452
-5 17
Helpers Absent Helpers Present
Helpers Absent Helpers Present
* Significant for both sexes for pup size
drawings by Elise Hammond2. Are there long-term fitness benefits for pups
with helpers?
a. Does presence/absence of helpers affect age at first
reproduction for pups?
b. Are there long-term effects of helpers on pup
reproductive success?Lifetime fitness estimates • Paternity & maternity known • Cause of death known • For late-life traits, included only individuals dying due to natural causes – Exceptions: censored/shot at old age • Lifetime reproductive success: sum of lifetime pups recruited (survived into Fall)
2a. Age at first reproduction is independent of helper
presence—but does differ between the sexes.
4.5 Females
Males
Age at first reproduction (yrs)
4
3.5
3
2.5
2
1.5 N = 103
P = 0.001
1
Pop'n Growth I Pop'n Growth II Pop'n Saturation
drawing by Elise HammondA g e a t la st re p ro d u ctio n (yrs) 9 A Females
2b. The relationship between
Males
8
7
lifetime fitness and presence
6
5 N = 39
of helpers differs between the
4
P = 0.003
sexes.
Helpers Absent Helpers Present
7 B
Reproductive lifespan (yrs)
15 Females
6
14 Males
5
Lifetime reproductive success
13
4
12
3 11
N = 39
P = 0.004 10
2
Helpers Absent Helpers Present
9
No. lifetime reproductive events
6 C 8
7
5
6
4
5 N = 34
P = 0.038
3 4
N = 39
Helpers Absent Helpers Present
P = 0.013
2
Helpers Absent Helpers Present
drawing by Elise HammondWhy the sex difference? H1: QUALITY OF SURVIVORS Females of the highest quality more likely to survive in presence of older siblings Selection less strong on males? H2: TRADE-OFFS Trade-off between helper-induced large size and reproductive lifespan in males • Males larger than females in general, especially in presence of helpers • May be cost to large size in males
SUMMARY 1. Do red wolves that delay dispersal “help”? • Effects of helpers on pup mass/size depend on ecological context, and persist into adulthood 2. Are there long-term fitness benefits for pups with helpers? • Helpers do not significantly advance/delay age at first reproduction for pups • Long-term fitness effects of helpers are sex-specific
Management Implications?
More study required to determine generality of these findings....
• Reintroduction candidates:
– Is bigger always better?
• Importance of Pack Stability
– Eastern wolf: management decisions can result in more
stable family units (Rutledge et al. 2010)
– Greater pack stability an important goal in red wolf, to
optimize female fitness?Acknowledgments
Coauthors:
– Dennis Murray, Trent University
– Jennifer Adams, University of Idaho
– Arthur Beyer, USFWS
– Todd Steury, Auburn University
– Lisette Waits, University of Idaho
Funding: USFWS
Red Wolf Recovery Team
Barron Crawford
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