Interannual Variation in Nut Abundance Is Related to Agonistic Interactions of Foraging Female Japanese Macaques (Macaca fuscata)

The importance of dominance status to foraging and ultimately survival or reproductive success in wild primates is known; however, few studies have addressed these variables simultaneously. We investigated foraging and social behavior among 17 adult female Japanese macaques (Macaca fuscata) on Kinkazan Island, northern Japan, from September to November in 2 consecutive years (2004 and 2005) to determine whether interannual variation in food availability was related to variation in agonistic interactions over food resources and the feeding behavior of individuals of different dominance rank. We compared energy obtained with daily energy requirements and also examined the effect of variation in feeding behavior on female survival and reproductive success. Fruiting conditions differed considerably between the 2 yr: of four nut-producing species, the nuts of only Torreya nucifera fruited in 2004, whereas all four species, particularly Fagus crenata, produced nuts in abundance in 2005. The abundance and average crown size of trees of Torreya nucifera were smaller than those of Fagus crenata, and there was a higher frequency of agonistic interactions during 2004, when dominant, but not subordinate, individuals were able to satisfy daily energy requirements from nut feeding alone through longer nut feeding bouts. In contrast, all macaques, regardless of their dominance rank, were able to satisfy their energy requirements by feeding on nuts in 2005. Subordinate macaques appeared to counter their disadvantage in 2004 by moving and searching for food more and maintaining larger interindividual distances. Several lower-ranking females died during the food-scarce season of 2004, and only one dominant female gave birth the following birth season. In contrast, none of the adult females died during the food-scarce season of 2005, and 12 females gave birth the following birth season. These findings suggest that an interaction between dominance rank and interannual variation in food availability are related to macaque behavior, survival, and reproduction.     

Effects of Yearly Change in Nut Fruiting on Autumn Home-range Use by <Emphasis Type="Italic">Macaca fuscata</Emphasis> on Kinkazan Island,Northern Japan

Temporal changes in food availability affect foraging success and ultimately reproductive success of animals. They include both seasonal and annual changes. Although many researchers have investigated food availability and the corresponding ranging behavior of primates, studies of yearly changes have been limited. We studied the effects of the fruiting of nuts of Fagus crenata, Zelkova serrata, and Torreya nucifera on the ranging behavior of Japanese macaques (Macaca fuscata) in autumn on Kinkazan Island, northern Japan, for 5 yr between 2000 and 2005 (excluding 2003). We divided the study area (3.3 km²) into 100 × 100-m quadrats to assess the distribution of nut-rich quadrats that contained high densities of nut-producing species. The home ranges of the monkeys contained more nut-rich quadrats than expected, and the difference was significant for 3 of 5 yr. Autumn home-range use was also affected by the distribution of nut production, although the effect differed by year: monkeys frequently used nut-rich quadrats in a Zelkova-year (2000) and in 1 Torreya-year (2001), whereas they nonselectively used nut-rich quadrats in 2 Fagus-years (2002 and 2005) and in another Torreya-year (2004). Thus, Japanese macaques flexibly change their autumn ranging behavior according to yearly changes in distribution of nut production.     

Marine prey processed with stone tools by burmese long‐tailed macaques (Macaca fascicularis aurea) in intertidal habitats

Long‐tailed macaques (Macaca fascicularis) feed opportunistically in many habitats. The Burmese subspecies (M. f. aurea) inhabits coastal areas in southwestern Thailand and Myanmar, and some of their populations have adapted lithic customs for processing encased foods in intertidal habitats. We investigated the diet of such macaques in Laemson National Park, Thailand, and identified the variety of foods they processed with stones. We conducted 36 shore surveys to study tool sites following feeding activity, during which we counted the minimum number of individual (MNI) food items found at each site. We identified 47 food species (43 animals and four plants), from 37 genera. We counted 1,991 food items during surveys. Nearly all were mollusks (n = 1,924), with the small remainder primarily consisting of crustaceans and nuts. The two most common foods, rock oysters (Saccostrea cucullata; n = 1,062) and nerite snails (Nerita spp.; n = 538), composed 80.2% of our sample. Four prey species comprised 83.2% of the sample (MNI = 1,656), S. cucullata (n = 1,062), Nerita chamaeleon (n = 419), Thais bitubercularis (n = 95), and Monodonta labio (n = 80). Macaques selected a wide variety of foods. However, they heavily concentrated on those that were abundant, easy to access, and sufficiently sized. The Burmese long‐tailed macaque stone‐processed diet, which focuses on intertidal marine prey, differs from Sapajus and Pan, who use stones primarily for encased nuts and fruits. In terms of diversity of foods exploited, coastal stone‐based predation by macaques resembles the diet of coastal‐foraging humans (Homo sapiens sapiens). Am J Phys Anthropol, 2012. © 2012 Wiley Periodicals, Inc.     

Impacts of Batrachochytrium dendrobatidis Infection on Tadpole Foraging Performance

Pathogen-induced modifications in host behavior, including alterations in foraging behavior or foraging efficiency, can compromise host fitness by reducing growth and development. Chytridiomycosis is an infectious disease of amphibians caused by the fungus Batrachochytrium dendrobatidis (Bd), and it has played an important role in the worldwide decline of amphibians. In larval anurans, Bd infections commonly result in reduced developmental rates, however, the mechanism(s) responsible are untested. We conducted laboratory experiments to test whether Bd infections reduced foraging performance of Grey Treefrog (Hyla chrysoscelis) and Fowler’s Toad (Anaxyrus [= Bufo] fowleri) tadpoles. In the first experiment, we observed foraging behavior of Bd-infected and uninfected tadpoles to test for differences in foraging activity. In a second experiment, we tested for differences in the ingestion rates of tadpoles by examining the amount of food in their alimentary track after a 3-hour foraging period. We hypothesized that Bd-infected tadpoles would forage less often and less efficiently than uninfected tadpoles. As predicted, Bd-infected larvae forage less often and were less efficient at obtaining food than uninfected larvae. Our results show that Bd infections reduce foraging efficiency in Anaxyrus and Hyla tadpoles, and that Bd differentially affects foraging behavior in these species. Thus, our results provide a potential mechanism of decreased developmental rates of Bd-infected tadpoles.     

Five-year study on the autumn food habits of the Asiatic black bear in relation to nut production

We studied the autumn food habits of the Asiatic black bear (Ursus thibetanus) from 1993 to 1997, based on 202 fecal samples in the Chichibu Mountains, central Japan. Nuts occupied the highest proportions of autumn foods (59.9–85.8% important values). Although the proportion of nuts of Quercus crispula, Fagus crenata and Fagus japonica varied greatly between the years, acorns of Q.crispula were most prevalent in four of the five years. We also determined the relative nut production of these three species by counting the number of nuts or cupules on the ground. Black bears consumed the nuts according to their relative availabilities. Nuts of Q.crispula appeared to be the most important food because: (i) these nuts were eaten in the highest proportion in four of the five study years; and (ii) even in poor years the bears consumed acorns of Q.crispula, whereas nuts of Fagus spp. were not consumed. We discuss the significance of alternative foods for black bears in relation to food tree diversity in the forest and the necessity for long-term studies examining the food habits of Asiatic black bears.     

Long-term variation in fruiting and the food habits of wild Japanese macaques on Kinkazan Island, northern Japan

We studied the relationship between the food habits of Japanese macaques (Macaca fuscata) and the availability of nuts (Fagus crenata, Zelkova serrata, Carpinus spp., and Torreya nucifera) on Kinkazan Island, northern Japan, from 1997 to 2005 to examine the long-term variations in both food habits and availability. The food habits of the monkeys showed clear seasonal changes: the staple foods were woody leaves and flowers in spring (May and June), woody leaves and seeds or fruits other than nuts in summer (July and August), nuts and seeds or fruits other than nuts in fall (September-November), and herbaceous plants in winter (December-April). The availability of nuts, combinations of masting species, and energy production varied among years. Food habits varied among years, but the magnitude of variability of food habits differed among seasons, with large variability during summer and winter, and small variability in spring. Food availability was poor in summer and winter, but in several years the monkeys were able to consume nuts during those seasons. We emphasize the importance of conducting long-term studies on both food availability and the food habits of animals in the temperate zone.     

Foraging efficiency of <Emphasis Type="Italic">Akodon azarae</Emphasis> under different plant cover and resource levels

The goal of this work was to determine how the foraging behaviour of Akodon azarae changes with predation risk and food availability in cropfield borders of Buenos Aires, Argentina. Our hypotheses were that A. azarae has a greater foraging efficiency in safe areas than in risky ones and that the foraging behaviour of A. azarae also depends on the level of resources. We measured giving-up densities (GUDs) and food consumption twice a year in artificial foraging patches (bottles with known amounts of millet seed) in covered and open areas and with two different levels of seed abundance. In both periods, GUDs were lower in the covered areas than in the open ones independently of food level. Consumption increased with food level in covered areas but not in open areas. Based on these results, we conclude that A. azarae appears to maximize its consumption depending on predation risk.     

Rapid shifting of foraging pattern by Yakushima macaques ( Macaca fuscata yakui ) in response to heavy fruiting of Myrica rubra

We describe short-term changes in foraging behavior by wild Yakushima macaques (Macaca fuscata yakui),which inhabit a warm-temperate broad—leaved forest on Yakushima Island (30°N, 131°E), Japan. Rapid changes of dietary composition, activity budget, and range use by the monkeys occurred from May to June, apparently associated with changes in the availability of the fruit of Myrica rubraBefore the fruit ripened, monkeys spent less time moving and more time feeding on many species of leaves, which accounted for 40% of feeding time. However, when M. rubrabegan to ripen, they fed intensively on the fruit, which accounted for three-fourths of feeding time,though the activity budget remained unaffected As fiuit of M. rubradecreased,the monkeys fed more on the fruit of other species and on insects, and spent more time moving at higher speeds. There marked shifts in foraging pattern occurred within only two months. In terms of moving cost and dietary quality,Yakushima macaques shifted their foraging pattern according to the availability of M. rubrafrom a “low-cost, low-yield” strategy to a “low-cost, high-yield” strategy, and then to a more costly strategy. The ability to make such rapid shifts in foraging pattern may allow the macaques to effectively use the highly variable food supply within their small range.     

Response of the European grapevine moth Lobesia botrana to somatosensory‐active volatiles emitted by the non‐host plant Perilla frutescens

The European grapevine moth Lobesia botrana Denis & Schiffermüller (Lepidoptera: Tortricidae) is a major pest on grapes worldwide. Attempts to develop control methods for this pest based on grape kairomones demonstrate limited success and studies indicate that a major limiting factor is overlap between synthetic kairomones and background odours in the vineyard. Behaviourally active compounds from non‐host plants may thus represent an effective alternative for monitoring and control methods. Extracts from food plants (i.e. from capsicum, garlic and peppermint, which elicit the so‐called somatosensory sensation) are traditionally used in agriculture for the control of pest insects. Among those plants, Perilla frutescens L. (Lamiales: Lamiaceae), native of Asia, contains compounds activating sensory ion channels in mammals, which are known to be involved in the perception of somatosensory compounds and are expressed in tortricid moth antennae. In the present study, in search of non‐host volatiles with potential application in pest control, essential oil metabolites isolated from P. frutescens are screened for biological activity on the olfactory system of L. botrana. The compounds (S)‐(?)‐perillaldehyde and isoegomaketone, which are released from different P. frutescens varieties, are identified by gas chromatography‐coupled electroantennographic detection. In a dual‐choice oviposition test, females show a preference for a combination of host odours and perillaldehyde, preferring this over a host‐plant odour bouquet alone. In Y‐tube olfactometer assays, virgin males show a higher level of activity in the presence of isoegomaketone, even if not significantly responsive to the compound.     

Foraging behavior and diet composition of Trimma caudomaculata and Trimma caesiura (Gobiidae) on coral reefs in Okinawa, Japan

The feeding habits of two small gobies, Trimma caudomaculata and T. caesiura, were surveyed on coral reefs in Okinawa, Japan. Both species actively exhibited foraging attempts beneath overhanging reef structures during the daytime, and fed on small animals, mainly copepods. Trimma caudomaculata formed feeding schools in water columns to swallow mainly Calanoida and Harpacticoida. Trimma caesiura stayed by themselves on the reef substratum and captured mainly Harpacticoida by taking short jumps into the water column. Diet compositions of these congeneric gobies may reflect differences in their foraging behaviors and use of microhabitats.     

Foraging ecology of Cookiecutter Sharks (<Emphasis Type="Italic">Isistius brasiliensis</Emphasis>) on pelagic fishes in Hawaii,inferred from prey bite wounds

The Cookiecutter Shark (Isistius brasiliensis) is an ecto-parasitic predator of numerous large pelagic fish and mammals. However, little is known of its foraging ecology due to its elusive foraging tactics in the pelagic environment. We used bite scar patterns on pelagic fishes landed at the Honolulu Fish Auction to assess some of the Cookiecutter Shark foraging habits. Swordfish (Xiphias gladius) had the greatest percentage of bites (87.9 ± 25.0% of individuals had healed scars) followed by Opah (Lampris guttatus, 33.0 ± 8.3% of individuals). Most fish with scars only had one Cookiecutter Shark bite per individual with the exception of Swordfish, which often had >5 bites per individual. Furthermore, Swordfish had a higher proportion of healed bite scars meaning they had been attacked while free-swimming. Seasonal changes in the probability of hooked fish being bitten by sharks were apparent for Swordfish, Bigeye Tuna and Opah. Based on bite scar diameter, larger Cookiecutter Sharks may preferentially attack Swordfish rather than the other species of pelagic fish. When taken in conjunction with diving behavior of pelagic fish, and fishing depths, the results add further support to the hypothesis that Cookiecutter Sharks perform diel vertical migrations.     

Feeding habits of chimpanzees (Pan troglodytes), red-tail monkeys (Cercopithecus ascanius schmidti) and blue monkeys (Cercopithecus mitis stuhlmanii) on figs in Budongo Forest Reserve, Uganda

Feeding habits of chimpanzees, red‐tail and blue monkeys on figs (Ficus) were studied in compartment N3 of Budongo Forest Reserve, western Uganda, from September 1997 to March 1998. The aim was to examine the spatial and temporal foraging habits of chimpanzees, red‐tail monkeys and blue monkeys on figs in the forest reserve. Both scan and focal sampling methods were used to assess the foraging habits of the primates. It was found that the primates fed on emerging leaves of Ficus mucuso Ficalho, F. varifolia Warb. and F. exasperata Vahl. They also preferred ripe fruits to emerging, young and unripe fruits. The primates spent 78% of the morning eating fruits and leaves and inhabited fig trees with fruits for about 4 h. Fig trees with ripe fruits attracted larger numbers of primate groups. It is concluded that information on the feeding habits of chimpanzees and monkeys is required in order to have a clear understanding of the social behaviour and pattern of movement of the primates and to assist in predicting the likely impacts of poor forest management, forest degradation and loss of food resources on their populations.     

The Impact of Physiological Demands on Foraging Decisions under Predation Risk: A Test with the Whelk Acanthina monodon

We study whether and how physiological demands affect foraging decisions under predation risk, by evaluating the effect of starvation on the rate of food consumption and prey‐size preferences and the potential trade‐off between starvation and predation risk on foraging behavior in the whelk Acanthina monodon, a gastropod inhabiting the intertidal rocky shores of central Chile. These whelks appear to adjust their foraging strategy to physiological (nutritional) demand and predation risk. Starvation reduced the effect of predation risk on the rate of food consumption by A. monodon. Thus, in the absence of the predator sea star, the rate of food consumption by starved and satiated whelks was similar. When a predator was present, starved whelks fed faster than satiated whelks. Our results indicate that foraging behaviour represents an integrated and hierarchical response to environmental conditions and the physiological conditions of the forager.     

Foraging costs and accessibility as determinants of giving-up densities in a swan-pondweed system

We measured the patch use behaviour of Bewick's swans (Cygnus columbianus bewickii) feeding on below ground tubers of fennel pondweed (Potamogeton pectinatus). We compared the swans’ attack rates, foraging costs and giving‐up densities (GUDs) in natural and experimental food patches that differed in water depth. Unlike most studies that attribute habitat‐specific differences in GUDs to predation risk, food quality or foraging substrate, we quantified the relative importance of energetic costs and accessibility. Accessibility is defined as the extent to which the animal's morphology restricts its harvest of all food items within a food patch. Patch use behaviours were measured at shallow (ca 0.4 m) and deep (ca 0.6 m) water depths on sandy sediments. In a laboratory foraging experiment, when harvesting food patches, the swan's attack rate (m³ s^?1) did not differ between depths. In deep water the energetic costs of surfacing, feeding and trampling were 1.13 to 1.21 times higher than in shallow water with a tendency to spend relatively more time trampling, the most expensive activity. Taking time allocation as measured in the field into account, foraging in deep water was 1.26 times as expensive as in shallow water. In the lake the GUD in shallow water was on average 12.9 g m^?2. If differences in energetic costs were the only factor determining differences in GUDs, then the deep water GUD should be 14.2 g m^?2. Instead, the mean GUD in deep water was 20.2 g m^?2, and therefore energetic costs explain just 18% of the difference in GUDs. At deep sites, 24% of tuber biomass was estimated to be out of reach, and we calculated a maximum accessible foraging depth of 0.86 m. This is close to the published 0.84 m based on body measurements. A laboratory experiment with food offered at a depth of 0.89 m confirmed that it was just out of reach. The agreement between calculated and observed maximum accessible foraging depths suggests that accessibility largely explains the remaining difference in GUDs with depth, and it confirms the existence of partial prey refuges in this system.     

Plasticity in Forest Tent Caterpillar Collective Foraging Schedules

Self‐organization can generate synchronized group activity without external triggering cues, and schedules of self‐organized collective activity can vary with environmental conditions. This plasticity can improve group members’ ability to meet their requirements in different environments. In colonial caterpillars, synchronized colony foraging schedules have been postulated to depend either on avoidance of visual predators or on temperature effects on ectotherm physiology. We examine the foraging schedule of forest tent caterpillars (Malacosoma disstria) under different constant conditions to distinguish between these hypotheses. Plasticity in the foraging schedule was tested by keeping colonies under different constant regimes of light and temperature. Digital video and tracking software were used to record the colony's alternation between quiescent and active bouts. The duration and frequency of bouts was compared between treatments. The schedule of synchronized colony activity was not affected by lighting, but it accelerated at higher temperature, because of a decrease in the duration of both active and quiescent bouts. Forest tent caterpillars’ foraging schedule thus depends on the time required to accomplish the tasks of food finding (active bouts) and food processing (quiescent bouts). As caterpillars are ectotherms, locomotion and digestion rates increase at higher temperature and both tasks are accomplished faster. The forest tent caterpillar and the congeneric eastern tent caterpillar (M. americanum) both exhibit self‐organized synchronized collective foraging, but environmental modulation of foraging schedule differs between these species, according to differences in social organization and thermal ecology. Eastern tent caterpillars maintain a fixed foraging schedule under varying temperatures and use the tent to maintain high metabolic rates. In the forest tent caterpillar, flexibility of the foraging schedule in accordance with changes in metabolism lessens the constraints imposed by collective foraging. Synchronous foraging, where entire social groups travel together to and from feeding sites, is thought to have several fitness advantages including improved food finding, recruitment to profitable food sources, anti‐predator defense and group thermoregulation between foraging expeditions.     

Costs and Benefits of Food Foraging for a Braconid Parasitoid

The costs and benefits of food foraging for the insect parasitoid, Phanerotoma franklini Gahan (Hymenoptera: Braconidae), were examined. Feeding benefited P. franklini by increasing longevity, but did not influence egg maturation. Costs of feeding are represented by the time required to locate and consume food. Field observations of starved wasps revealed that wasps spent approximately 25% of their time grazing on substances on the surface of cranberry foliage. However, our initial laboratory tests to determine the value of these substances were inconclusive. We also examined how grazing behavior integrated with host foraging by comparing the attack rate of fed and unfed wasps held under different host densities. While feeding status did not affect the mean attack rate of wasps, starvation enhanced the probability that a wasp will engage in movement over the host plant foliage. We conclude that feeding benefits P. franklini by increasing longevity, that travel time to food sources is likely to be low, and that the observed food-foraging behavior does not appear to influence host-foraging efficiency.     

Sooty mangabeys scavenge on nuts cracked by chimpanzees and red river hogs—An investigation of inter‐specific interactions around tropical nut trees

Carrion scavenging is a well‐studied phenomenon, but virtually nothing is known about scavenging on plant material, especially on remnants of cracked nuts. Just like meat, the insides of hard‐shelled nuts are high in energetic value, and both foods are difficult to acquire. In the Taï forest, chimpanzees (Pan troglodytes) and red river hogs (Potamochoerus porcus) crack nuts by using tools or strong jaws, respectively. In this study, previously collected non‐invasive camera trap data were used to investigate scavenging by sooty mangabeys (Cercocebus atys), two species of Guinea fowl (Agelestres meleagrides; Guttera verreauxi), and squirrels (Scrunidae spp.) on the nut remnants cracked by chimpanzees and red river hogs. We investigated how scavengers located nut remnants, by analyzing their visiting behavior in relation to known nut‐cracking events. Furthermore, since mangabeys are infrequently preyed upon by chimpanzees, we investigated whether they perceive an increase in predation risk when approaching nut remnants. In total, 190 nut‐cracking events were observed in four different areas of Taï National Park, Ivory Coast. We could confirm that mangabeys scavenged on the nuts cracked by chimpanzees and hogs and that this enabled them to access food source that would not be accessible otherwise. We furthermore found that mangabeys, but not the other species, were more likely to visit nut‐cracking sites after nut‐cracking activities than before, and discuss the potential strategies that the monkeys could have used to locate nut remnants. In addition, mangabeys showed elevated levels of vigilance at the chimpanzee nut‐cracking sites compared with other foraging sites, suggesting that they perceived elevated danger at these sites. Scavenging on remnants of cracked nuts is a hitherto understudied type of foraging behavior that could be widespread in nature and increases the complexity of community ecology in tropical rainforests.     

Foraging strategies of yakushima macaques (Macaca fuscata yakui )

I investigated the activity budget and diet of Yakushima macaques (Macaca fuscata yakui,)in warm temperate broad- leaved forest of Yakushima, Japan. Both time spent feeding and time spent moving varied considerably between half- months. However, total time spent in active behaviors— feeding time plus moving time— was stable. The composition of the diet also showed considerable variation between half- months. The macaques fed mainly on fruits, seeds,mature leaves, fallen seeds, flowers, and young leaves, each of which accounted for more than 30% of feeding time in at least 1 half- month. They also ate insects and fungi, but each of them comprised ≤ 25 and ≤ 8% of feeding time in any half- month, respectively. Time spent feeding on mature leaves, young leaves, flowers, or fallen seeds is positively correlated with total time feeding and is negatively correlated with time moving. In contrast, time feeding on fruits, seeds, insects or fungi is negatively correlated with time feeding and is positively correlated with time moving. Foraging on foods that have a low energy content, a high density, and a relatively even distribution— mature leaves— or that need much manipulation to be processed— flowers and fallen seeds— increased feeding time, while foraging on foods for which monkeys must search intensively in the forest— fruits, seeds, insects, and fungi— led to increased moving time. I examined foraging strategies of Yakushima macaques in terms of moving costs and the quality of food items. Regarding time feeding on fruits, which have more energy and may need less manipulation than other foods, as a benefit, and moving time as a cost, they seemed to employ a strategy that balanced the costs and benefits of foraging.     

Foraging site use and interspecific competition between bluegills and golden shiners

Synopsis Laboratory experiments examined the foraging performances of a dietary generalist, bluegill,Lepomis macrochirus, and a dietary specialist, golden shiner,Notemigonus crysoleucas, as they fed from devices simulating four foraging sites (bottom substrate, water column, submerged macrophytes, and water surface). Fishes foraged in monospecific and mixed-species groups of two and four individuals. For monospecific groups, foraging rates of bluegills did not differ among the four sites, but golden shiners had significantly higher rates on bottom and midwater sites than on plant and surface sites. The size of monospecific groups did not affect foraging rates of either species. In mixed-species trials, bluegills removed more food items than golden shiners from plant and surface sites in two- and four-fish groups and from bottom sites in two-fish groups. Bluegills' foraging performances improved with experience, golden shiners' performances did not. Experimental results are discussed with respect to interactions between bluegills and golden shiners in natural assemblages.     

Foraging segregation by sex and age class in the Guadalupe fur seal from Guadalupe Island,Mexico

A proper assessment of the foraging habits of the Guadalupe fur seal (GFS; Arctocephalus townsendi) is a priority to better understand its recovery, in which the potential for intraspecific competition for prey and space resources is expected to lead to segregation. This study aimed to determine the foraging habits of different sex and age classes. A total of 146 GFS fur samples was collected at Guadalupe Island, Mexico (2014–2020) for stable isotopes (δ¹³C and δ¹⁵N) analysis. Isotopic areas were created (SIBER package in R). Significant isotopic differences were observed between classes. Male (3.6‰²) and female (3.0‰²) juveniles had the largest isotopic areas due to a greater foraging dispersion. Adult females showed the lowest mean δ¹⁵N value (16.1‰ ± 0.5‰) due to foraging trips that are mostly performed towards high latitudes. Except for pups, adult and subadult males presented the highest mean δ¹⁵N (17.4‰ ± 0.4‰) and δ¹³C values (−17.0‰ ± 0.8‰) due to a possible higher trophic level and coastal foraging habits, whereas pups presented the highest mean δ¹⁵N value (17.6‰ ± 0.3‰) because of lactation, which reflects their mothers δ¹⁵N signal plus their own enrichment. Our findings suggest a segregation explained by differences in life history, energy requirements, and a possible strategy to avoid competition.