Seasonal food habits of the endangered long-tailed chinchilla (Chinchilla lanigera): the effect of precipitation

Mamm. biol. 67 (2002) 167±175                                                  Mammalian Biology
ã Urban & Fischer Verlag                                    Zeitschrift fuÈr SaÈugetierkunde

Original investigation
Seasonal food habits of the endangered long-tailed
chinchilla (Chinchilla lanigera):
the effect of precipitation
Departamento de BiologõÂa, Universidad de La Serena, La Serena and Departamento de Ciencias BaÂsicas,
Universidad de Los Lagos, Osorno, Chile

Receipt of Ms. 19. 04. 2001
Acceptance of Ms. 19.09. 2001

Based on the content of feces, we studied the food habits of the endangered rodent Chinchilla lani-
gera. On a seasonal basis, during two years of contrasting rain levels (1992 = 242 mm;
1993 = 123 mm), we collected chinchilla feces from El Cuyano ravine, adjacent to the Chinchilla
National Reserve in north central Chile (31° 29' 10.8'' S, 71°03' 43.9'' W). The main plant species
eaten was the perennial graminoid Nassella chilensis. Chinchillas showed a broader trophic niche
during the rainy year, than during the dry year, consuming 55.5 and 40.7% of the 38 and 27 plants
available, respectively. Within the wet year the diet differed less between winter and summer (Horn
similarity index R0 = 0.58) than within the dry year (R0 = 0.83). Between years, the diet differed
more during winters (R0 = 0.20) than during summers (R0 = 0.52). Chinchillas are folivorous, using
a feeding pattern of a generalist species. The opportunistic feeding behavior of chinchillas may be
an adaptation to the harsh conditions and high variability in food availability triggered by fluctua-
tions in rainfall among years in the arid north central Chile.

Key words: Chinchilla lanigera, food habits, Chile, rainfall

The long-tailed chinchilla (Chinchilla lanigera          gered and known only from the locality of
Molina, 1782) is a medium-sized hystricog-               Auco (31° 38' S, 71° 06' W), in the Chinchilla
nath rodent endemic to north central Chile.              National Reserve and its surroundings, and
These chinchillas had a relatively wide distri-          from a colony north of Coquimbo (29° 33' S,
bution in the past, ranging in the rugged                71°04' W; JimeÂnez 1995). However, despite
coastal mountains from the Choapa River                  protection in the reserve, chinchilla abun-
(32° S) north to Potrerillos (26° S; JimeÂnez            dance is still declining (JimeÂnez 1990).
1996). Because of over-exploitation for its              Information on the ecology and natural his-
valuable fur, it was almost extirpated by the            tory of these chinchillas is scant. They are
end of the 19th century and was considered               herbivorous, live in discrete colonies, and
extinct until the 1970's (JimeÂnez 1994). This           are nocturnal (JimeÂnez 1995). Ecological
chinchilla is currently considered endan-                densities (within colonies) vary widely in

1616-5047/02/67/03-167 $ 15.00/0.
168        A. CORTEÂS et al.

time and space, ranging between 0.9 to                Reserve, in AucoÂ, north central Chile. The climate
10.7 individuals/ha (JimeÂnez 1990). Most of          is mediterranean-arid (Hajek and Di Castri
the scattered colonies are located on steep           1976), with sparse rainfall concentrated during
                                                      the cold austral winter (88% between May and
and dry equatorial-facing slopes, where the
                                                      August). Mean annual precipitation for 10 years
chinchillas use the succulent bromeliad,              is about 200 mm (range 86±513 mm), but exhibits
Puya berteroniana, rock crevices, and                 high interannual variability (Fuentes et al.
boulder piles as refugia (JimeÂnez 1995).             1988). Mean annual temperature is between 15
Food habits of chinchillas are poorly known.          and 16 °C, reaching freezing temperatures during
Accounts on their diet have been qualitative          winter nights and over 40 °C during summer
and non-rigorous (Mohlis 1983). Based on              days.
the analysis of feces collected in the Chin-          The rugged topography shapes the landscape
                                                      forming interspersed slopes, ravines, and flatlands.
chilla National Reserve in north central
                                                      Elevations range from 400 to 1,700 m. The vege-
Chile, Serra (1979) first reported chinchilla         tation is dominated by thorn-scrub species. Spe-
diet quantitatively. Combining information            cies composition and density af plants depend on
from 3 years, she found that chinchillas had          slope, aspect, substrate, water availabitity, and
a diverse diet, fed mostly on shrub leaves,           anthropogenic disturbance (Gajardo 1978).
and that species composition in the diet var-         Slopes that face north (equatorial) receive higher
ied considerably among seasons. More re-              solar radiation, and have sandy soils with scat-
cently, JimeÂnez (1990) estimated the diet of         tered gravel patches and frequent rock outcrops.
                                                      Because of the xeric character of these slopes
the same population using cafeteria tests
                                                      grasses are scarce (mainly Nassella chilensis and
and fecal analysis. Interestingly, he found           Stipa plumosa), but cacti (Echinopsis chilensis,
that when offered fresh and dead leaves of            Opuntia ovata), bromeliads (Puya berteroniana),
several plant species, chinchillas preferred          and sclerophyllous shrubs including Bahia ambro-
the dead and dried leaves, mainly from herb           sioides, Cordia decandra, Bridgesia incisaefolia,
species. Chinchillas showed no interest in            and Flourensia thurifera are abundant. In con-
seeds and pods of native plants. According            trast, slopes that face south (polar) receive less ra-
to JimeÂnez (1990), wild chinchillas feed an          diation and are thus more mesic. Grasses here
                                                      are more abundant, cacti and bromeliads are ab-
up to 24 plant species, mainly herbs, and
                                                      sent, and a different assemblage of shrubs pre-
their diet changes substantially between              vails (Adesmia spp., Porlieria chilensis, Colligua-
sites and during the year.                            ja odorifera, and Proustia spp.; JimeÂnez et al.
To know the dietary requirements and its              1992).
dependence on the availability of food                Collection of feces and reference plant samples:
items in the field, especially when the avail-        Fresh fecal pellets were sampled in the field for
abilities change in space and time, is crucial        three days in each of the four seasons during two
for understanding the trophic ecology and             years of cantrasting precipitation regimes: in
                                                      1992, when it rained 242 mm (a ªwetº year) and
behavior of a wild species. This is especially
                                                      in 1993 when it rained 123 mm (a ªdryº year).
important for implementing conservation               Then, samples were taken to the laboratory and
plans for endangered species, such as the             dried at 60 °C for 48 to 72 h.
chinchilla that lives in a food-poor and              On a seasonal basis we sampled leaves, stems, and
harsh environment in which resources fluc-            flowers of all plant species present at the study
tuate enormously in space and time (JimeÂ-            site. Herbs, shrubs, and succulents were deter-
nez et al. 1992). To bridge this gap, we stud-        mined by comparisons with the plant collection
ied the chinchilla diet throughout two years          deposited at Universidad de La Serena. A micro-
                                                      histological slide collection was prepared follow-
of contrasting rainfall.
                                                      ing Sparks and Malechek (1968). Black and
                                                      white pictures were obtained from all slides sam-
Material and methods                                  From the more than 100 fecal pellets collected
                                                      during each season, we randomly selected 40 for
Study area: We sampled fresh chinchilla feces         dietary analysis. From each group we obtained
at El Cuyano Bajo ravine (31° 29' 10.8'' S,           10 slide preparations (Baumgartner and Martin
71° 03' 43.9'' W), close to the Chinchilla National   1939). In turn, 10 fields from each slide were stud-
Food habits of chinchilla    169

ied under a Leitz microscope with 36-x magnifica-     the unidentified material and fibers, during
tion, which was equipped with a 7 ´ 7-grid quad-      the wet year herbs made up the bulk of the
rant. Fields with less than 50% of the area cov-      diet, followed in importance by shrubs
ered by plant material were disregarded. Plant
                                                      (Tab. 1). The reverse occurred during the
fragments were compared to the samples in the
voucher slide collection. Diet composition was es-    dry year. The amount of fiber and undeter-
timated by using the relative surface covered by      mined material ingested was remarkably
each food item in the fields. Then, we computed       similar between years. The seed component
the frequency of occurrence of each item in the       in the chinchilla diet was minor and almost
fields examined (Meserve 1976).                       absent from the diet during the wet year,
Trophic niche breadth: We used the Shannon-           but their importance increased during the
Weaver index (Shannon and Weaver 1949) to es-         dry year (Tab. 1).
timate the diet diversity as: H' = ±R pi log pi,
                                                      The same yearly pattern detected for the
where pi is the proportion of items of species i in
the sample (estimated as pi = ni/N; where ni is       abundance of plant groups and parts was
the number of items af species i out of all items     found for the species composition in the
across species, which is N). Diet diversity in-       chinchilla diet (Tab. 1). The diet included
creases as the index increases.                       more species during the wet year than dur-
Diet similarity: To compare the similarity of diets   ing the dry year, incorporating a total of 21
between seasons (within years) and between            and 11 species, respectively. More shrub
years (for the same seasons) we used the Horn         species than herbs were consumed during
(1966) overlap index as: R0 = H4' ± H3'/H4' ± H5',
                                                      both years, with the exception of the winter
where H3', H4, and H5' are computed based on
the Shannon-Weaver index (as in Brower and            and spring of the wet year (Tab. 1).
Zar 1984). The index ranges from 0 (complete          By species, as well as by percent of occur-
dissimilitude) to 1 (highest diet similarity).        rence, herbs were consumed more during
                                                      the wet than during the dry year (Tab. 1).
                                                      The reverse was true for shrubby species.
Results and discussion                                During the dry year there were 3 plant spe-
                                                      cies that made up most of the recognized
The dietary analysis of chinchilla based an           food items: the succulent P. berteroniana
the contents of feces indicates that the dif-         the herb N. chilensis, and the shrub Bridge-
ferent plant life forms eaten varied mark-            sia incisifolia. These species showed up in
edly among seasons and between years                  the diet consistently throughout the seasons
(Tab. 1). Overall, fibers made up most                and may be used by chinchillas when other
(> 66%) of the diet in both years and in all          plants are less available.
seasons. These fibrous items are extremely            It appeared that chinchillas are capable of
difficult to identify and may correspond to           using a wide range of plants when these
highly lignified plant parts such as bark             are available in the environment. Out of
and woody stems of shrubs and of the suc-             the 38 plant species detected in the field
culent agave-like bromeliad Puya berteroni-           during the wet year, chinchillas consumed
ana. Herbs and shrubs followed in impor-              at least 55.3% of these plant species
tance in the chinchilla diet (Tab. 1).                (Tab. 1). When fewer plants (27 species)
Identified succulents made up only a small            were available due to a lack of rain, the ro-
fraction af the chinchilla diet, and were             dents showed a much narrower diet
eaten in a non-predictable way throughout             (11 species), ingesting only 40.7% of the
the two years. The same was true for seeds,           plants available. This same trend was ob-
the least represented food category in the            served in the niche breadth index. On aver-
diet.                                                 age, an H' of 0.78 was found during the wet
Yearly variation of the chinchilla diet: The          year, whereas H' was 0.65 during the dry
proportion of plants eaten by chinchillas             year.
differed between the two years. Herbs and             Seasonal changes in the chinchilla diet: The
shrubs were incorporated into the diet                abundance of different plant life forms var-
throughout both years. Not accounting for             ied highly across seasons in the chinchilla
170         A. CORTEÂS et al.

Table 1. Food items consumed seasonally (%) by Chinchilla lanigera and plant species availablities (AV) in north
central Chile during a wet (1992) and a dry year (1993). Totals by category are shown in parentheses. The H'
Shannon-Wiever index of food diversity is shown at the bottom of the table.1: FA = fall, WI = winter, SP = spring,
SU = summer, AV = availability. [2: ± = not detected. 3: + = present, - = not found, na = not assessed.]

                                   Wet year                                             Dry year
                   FA       WI      SP        SU      AV               FA       WI      SP         SU     AV

 SHRUBS            (17.5) (5.2)     (2.1)     (4.0)                    (8.8)    (7.3)   (12.2) (7.7)
 Astephanus        0.8      ±2      ±         ±       +3               ±        ±       ±          ±      +
 Cordia decandra   ±        ±       ±         0.1     +                ±        ±       ±          ±      +
 Heliotropium      3.1      1.9     ±         1.8     +                2.9      0.3     ±          ±      +
 Lobelia           1.0      1.3     0.3       0.3     +                ±        0.8     ±          ±      +
 Baccharis         ±        ±       ±         ±       +                ±        ±       ±          ±      +
 Flourensia        ±        ±       ±         ±       +                ±        ±       ±          ±      +
 Gutierresia       ±        ±       ±         ±       +                ±        ±       ±          ±      +
 Proustia          3.3      1.1     ±         ±       +                1.2      0.3     1.7        ±      +
 Ephedra andina    ±        ±       ±         1.6     +                ±        ±       ±          1.3    +
 Colliguaja        ±        0.9     1.3       ±       +                ±        0.1     1.5        ±      +
 Krameria          ±        ±       ±         ±       +                ±        ±       ±          ±      +
 Adesmia           1.5      ±       ±         0.2     +                ±        ±       ±          ±      +
 Anisomeria        ±        ±       ±         ±       +                ±        ±       ±          ±      +
 Bridgesia         2.7      ±       ±         ±       +                4.7      5.5     6.4        6.0    +
 Cestrum parqui    ±        ±       ±         ±       +                ±        ±       ±          ±      +
 Lycium chilense   ±        ±       0.2       ±       +                ±        0.2     2.2        ±      +
 Porlieria         5.1      ±       0.3       ±       +                ±        0.1     0.4        0.4    +
Food habits of chinchilla            171

Table 1. (Continued)

                                    Wet year                               Dry year
                   FA       WI      SP         SU    AV   FA       WI      SP         SU      AV

 HERBS             (9.7)    (3.7)   (23.5) (4.2)          (2.1)    (5.0)   (8.2)      (3.5)
 Adiantum          7.0      ±        1.4       ±     +    ±        ±       ±          ±       ±3
 Notholaena        ±        ±       ±          ±     +    ±        ±       ±          ±       ±
 Rhodophiala       ±        0.4      0.3       ±     +    ±        ±       ±          ±       ±
 Caesalpinia       ±        ±       ±          ±     +    ±        ±       ±          ±       ±
 Moscharia         ±        ±        2.1       ±     +    ±        ±       ±          ±       ±
 Erodium sp.       ±        0.4      1.6       ±     +    ±        ±       ±          ±       ±
 Hordeum           ±        ±       ±          ±     +    ±        ±       ±          ±       ±
 Nassella          1.2      1.4     16.0       4.2   +    2.1      4.9     8.2        3.5     +
 Stipa plumosa     ±        ±       ±          ±     +    ±        ±       ±          ±       +
 Pasithaea         ±        ±       ±          ±     +    ±        ±       ±          ±       +
 Pleurophora       ±        ±        0.6       ±     +    ±        ±       ±          ±       +
 Oxalis carnosa    1.5      1.5      0.8       ±     +    ±        0.1     ±          ±       ±
 Plantago          ±        ±       ±          ±     +    ±        ±       ±          ±       +
 Galium aparine    ±        ±       ±          ±     +    ±        ±       ±          ±       ±
 Llagunoa          ±        ±       ±          ±     +    ±        ±       ±          ±       +
 Apium             ±        ±        0.3       ±     +    ±        ±       ±          ±       ±
 Glandularia       ±        ±        0.4       ±     +    ±        ±       ±          ±       ±
172        A. CORTEÂS et al.

Table 1. (Continued)

                                      Wet year                                                Dry year
                  FA       WI         SP         SU         AV             FA      WI         SP         SU      AV

 SUCCULENTS       (4.2)    (1.0)      (0.0)      (3.2)                     (4.6)   (2.7)      (4.3)      (0.4)
 Puya             4.2          1.0    ±              3.2    +               4.6        2.7     4.3        0.4    +
 Echinopsis      ±         ±          ±          ±          +              ±       ±          ±          ±       +
 Eulychnia acida ±         ±          ±          ±          +              ±       ±          ±          ±       +
 Opuntia ovata ±           ±          ±          ±          +              ±       ±          ±          ±       +
 OTHERS           (68.2) (90.1) (74.4) (88.6)                              (84.5) (85.0) (75.3) (88.4)
 Seeds            ±            1.0    ±          ±          na             ±           0.2     4.1        1.0    na
 Unrecognized      2.4     10.3        6.4           8.4    na             12.9        9.1     3.6       10.8    na
 Fibers           66.2     78.8       68.0       80.2       na             71.6    75.7       67.6       76.6    na
 TOTAL NUMBER 11               9      13             7                      5      10          7          5

 Shannon-Wiever    0.91        0.91    0.64          0.65   na              0.68       0.69    0.72       0.51   na

diet (Tab. 1). This variability produced no                      most of the diet was made up of perennial
recognizable patterns when comparing the                         shrubs (Tab. 1).
two years sampled. No patterns were de-                          The food items eaten that had the largest
tected in the numbers of species eaten                           variability in amount and diversity within
across the seasons when comparing years                          the years were the herbs and shrubs,
either (Tab. 1). However, the diet breadth                       whereas the succulent P. berteroniana and
during the spring of both years showed in-                       the graminoid N. chilensis were eaten on a
teresting opposite trends. Although the diet                     more regular basis. Given its 70 to 80%
during the spring of the wet year included                       water composition, it is likely that P. berter-
the largest number of plant species, the                         oniana represents a predictable water
niche breadth index was the narrowest                            source for chinchillas throughout the year
(Tab. 1). Conversely, the relatively few spe-                    (CorteÂs, unpubl. data). It is unfortunate
cies consumed during the dry year rendered                       that cacti tissue do not show up in diet ana-
the broadest niche breadth during that year.                     lysis. There were at least 3 cactus species
This is most likely reflected by the less-even                   present at the site and it is well known that
diet during the spring of the wet year, which                    chinchillas eat cacti fruits, which are also
resulted from the disproportionate high                          mostly made up of water (JimeÂnez 1990;
consumption of N. chilensis (16%) by                             see also Serra 1979).
chinchillas. In contrast, during the dry year                    Herb species are most affected by the
most food items were eaten in a more pro-                        amount of rain over the short term (Gu-
portional way. In fact, when herbs were                          tieÂrrez et al. 1997). Thus, during the wet
scarce in the environment (only 6 of the                         year, it was likely that, compared to the
17 species detected) during the dry year,                        dry year, herbaceous plants were plentiful
Food habits of chinchilla    173

and therefore available to chinchillas. This     eteria tests on 3 wild chinchillas kept in
response was also shown by the amount            captivity for a short time period. He of-
and the diversity of herbs consumed by           fered seeds of 8 shrubby species native to
chinchillas during the spring of the wet year    the area, but unlike findings in this study
(Tab. 1). Indeed, N. chilensis, which ap-        and that of Serra (1979), he found no con-
peared as the most consumed plant species        sumption by chinchillas. From the other
by chinchillas during the spring of 1992, is     23 native species' leaves offered to the
a graminoid, the growth of which is depend-      chinchillas, JimeÂnez (1990) detected con-
ent upon the amount of rainfall (GutieÂrrez      sumption of 56.5% of them. The most fre-
et al. 1997). By comprising the bulk of the      quently eaten items were leaves of the
herbs consumed by chinchilla during the          herbs Pasithaea coerulea and N. chilensis.
spring of the wet year, when availability of     We did not detect P. coerulea in the diet,
plant species and amount of green biomass        although it was present in the field in the
are high, N. chilensis appears to be a pre-      two years of the study. In accordance with
ferred diet component. Even when plants          our findings, JimeÂnez (1990) also found
were scarcer, as in 1993, N. chilensis was       high consumption of N. chilensis. He noted
still an important component of the chin-        that when he offered dead and fresh leaves
chilla diet. During the springs, when the in-    of the same plant, chinchillas often pre-
gestion of more fleshy species with a higher     ferred the dead leaves.
water content increased, fibrous plants with     It is important to note here that we did not
low digestibility and lower energetic and        distinguish different structures or parts for
nutritious value (Veloso and Bozinovic           the same plant species eaten by chinchillas.
1993) decreased (Tab. 1). Thus, N. chilensis     Chinchillas may have consumed selectively
may be an item of high energetic and nutri-      different plant structures in different sea-
tious value, perhaps necessary when gesta-       sons or for different plant availabilities in
tion and lactation take place (JimeÂnez          the field as reported by Serra (1979). Our
1990).                                           study could not evaluate any of these po-
To our knowledge, the only other diet study      tential scenarios.
of this chinchilla species in the wild was       Diet similarity: Because of the lack of quan-
conducted by Serra (1979) in the nearby          titative plant availabilities during the years
Chinchilla National Reserve. She also found      sampled, we could not infer food prefer-
high variation in the plant species composi-     ence by chinchillas. We did, however, calcu-
tion and amounts eaten during the different      late the degree of diet similarity within
seasons. Her differing results may have          years and between years. Comparing con-
been due to local plant availabilities or        trasting seasons (i. e., summer vs. winter),
rainfall. However, the data are hardly com-      similarity was lower during the wet year
parable, given that her samples were col-        (R0 = 0.58) than during the dry year
lected in three different years, with rainfall   (R0 = 0.83). This is consistent with the low-
amounts unreported. The technique that           er number of plant species available during
Serra (1979) used was not sufficiently lu-       the dry year (Tab. 1).
cid.                                             In contrast, higher number of plant spe-
Preliminary analysis on the chinchilla diet      cies during the summer of the wet year
from the Chinchilla National Reserve (Ji-        compared with that of the winter, could
meÂnez 1990) using a method similar to this      render a consumption of different plant
study, showed that during 1987 and 1988          species by chinchillas, and thus results in
the chinchilla diet was highly variable          a lower diet similitude. On the other
among seasons and also between sites.            hand, the low similitude found between
The diet was diverse, including between 6        the two winters (R0 = 0.20) compared to
and 12 plant species, well in line with the      that of the two summers (R0 = 0.52),
5 to 13 plant species detected in this study.    points in the same direction as above:
JimeÂnez (1990) also conducted several caf-      rainfall appears to trigger plant produc-
174       A. CORTEÂS et al.

tion that is detected in the chinchilla diet         Acknowledgements
during the summer.
Based on the above analysis, we conclude             We are grateful to the Chilean Forest Service
                                                     (IV Region, Chile) for logistical support, and to
that chinchilla is a generalist and opportu-
                                                     ranger Baldomero PenÄa for his knowledge and
nist herbivorous rodent, incorporating her-          help in the field. We thank Ronald Gettinger
baceous plants into its diets when available.        and three other reviewers for their constructive
This is seen as a dietary adaptation to an           comments. The help of Gina Arancio for provid-
ecosystem that is highly variable in rainfall        ing access to the herbarium of Universidad de La
and thus primary production, a characteris-          Serena, and for identifying the plant species is ap-
tic of the arid shrublands of north central          preciated. Katja Kunz kindly translated the ab-
Chile.                                               stract into German. This research was funded by
                                                     grants FONDECYT 1981122 and DIULS 120-2-81.

Saisonale ErnaÈhrungsgewohnheiten des gefaÈhrdeten Chinchilla (Chinchilla lanigera):
Der Effekt von Niederschlag
Anhand der Zusammensetzung von Kotproben studierten wir die ErnaÈhrungsgewohnheiten des ge-
faÈhrdeten Nagers Chinchilla lanigera. In zwei Jahren unterschiedlicher NiederschlagshaÈufigkeit
(1992: 242 mm; 1993: 123 mm) sammelten wir in verschiedenen Jahreszeiten Chinchilla-Kotpro-
ben in der El Cuyano-Schlucht, die an das Chinchilla-National-Reservat im noÈrdlichen Zentral-Chile
(31° 29' 10.8'' S, 71° 03' 43,9'' W) angrenzt. Die wesentliche Futterpflanze ist die mehrjaÈhrige Gra-
mineen-Art Nassella chilensis. Chinchillas zeigten waÈhrend des niederschlagsreicheren Jahres eine
weitere trophische Nische als waÈhrend des Trockenjahres. Beobachtet wurden die Nutzung von
55,5% bzw. 40,7% von jeweils 38 bzw. 27 verfuÈgbaren Pflanzen. WaÈhrend des niederschlagsreiche-
ren Jahres variierte die Nahrungszusammensetzung zwischen Winter und Sommer weniger (Horn-
Index R0 = 0,58) als waÈhrend des Trockenjahres (R0 = 0,83). Im mehrjaÈhrigen Vergleich sind groÈûe-
re Unterschiede im Winter (R0 = 0,20) als im Sommer (R0 = 0,52) zu beobachten. Chinchillas sind
herbivore Generalisten, deren opportunistische ErnaÈhrungsgewohnheiten als Anpassung an die Ari-
ditaÈt und die niederschlagsbedingten Ønderungen im Nahrungsangebot im noÈrdlichen Zentral-Chile
zu deuten sind.

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