Foraging Patterns Research Articles

Social and Seasonal Factors Contribute to Shifts in Male African Elephant (Loxodonta africana) Foraging and Activity Patterns in Kruger National Park, South Africa.

Simple SummaryAfrican savannah elephants are able to greatly modify the vegetation around them through their foraging activities. Accordingly, studying the factors that affect elephant foraging behaviour during different seasons are important to understand their impact on the environment and will also aid in predicting how elephants might react to potential threats such as climate change and land transformation. This article aimed to reinforce current knowledge regarding elephant foraging behaviour by examining how the behaviour is affected across (a) season (wet versus dry); (b) time of day (before or after noon); (c) presence or absence of other elephants; and (d) reproductive state; for six adult elephant bulls monitored in Kruger National Park. Results indicated that elephant foraging behaviour is indeed affected by seasonal and social factors. This highlights how these animals are able to adjust their foraging behaviour during the day to aid in thermoregulation, or during different seasons to fulfil their nutritional requirements. Furthermore, this study opens the door for further research regarding how reproductive activity affects the foraging behaviour of male elephants.African savannah elephants (Loxodonta africana) are well-known as ecosystem engineers with the ability to modify vegetation structure. The present study aimed to examine how male elephant foraging behaviour is affected across (a) season (wet versus dry); (b) time of day (before or after noon); (c) presence or absence of other elephants; and (d) reproductive state (musth versus no musth). Six radio-collared adult elephant bulls were observed twice per week from June 2007–June 2008 in Kruger National Park (KNP), South Africa. Using generalized linear mixed effect modeling, results indicate that elephant bulls graze more during the wet season and browse more during the dry season. To potentially offset the costs associated with thermoregulation during the heat of the day, KNP elephants spent more time foraging during the morning, and more time resting during the afternoon. Male elephants also foraged significantly less when they were associated with females compared to when they were alone or with other males. This is likely due to male–female associations formed mainly for reproductive purposes, thus impeding on male foraging behaviours. In contrast, the condition of musth, defined by the presence of related physical signs, had no significant effect on foraging behaviour.

Signs of Genetic and Morphometric Population Differentiation in Small Planctivorous Seabird, Parakeet Auklet Aethia psittacula, Reinforces Linkage between Population Structure and Migratory Strategy

Study of population genetic structure is essential for insight in species biology, but mechanisms of its formation and factors influencing it remain insufficiently understood. Here we analyzed differentiation among populations in small colonial seabird of North Pacific, the Parakeet Auklet Aethia psittacula, which was previously considered as a monomorphic species. We compare our results with data on congeneric species to investigate the most important factors affecting the process of population differentiation in Aethini. We analyzed morphometric measurements, mitochondrial DNA control region fragment and microsatellite loci from six Parakeet Auklet colonies spanning the breeding range. Although results of microsatellite variability analysis did not reveal differences between birds from different colonies, results of control region variability and morphometric analyses testified for a slight but significant differentiation between birds from the Aleutian Islands and other parts of their range. They were significantly smaller in most linear parameters measured and had higher body condition (expressed as the scaled mass index). The results of mtDNA analysis and discrepancy between different types of genetic markers indicated that birds from Aleutian Islands and from the other parts of their breeding range probably originated from different refuges and the differentiation of mitochondrial lineages between them took place around 100 000 years ago. Our results and conclusions from the comparison with congeneric species indicated that foraging and migration patterns seem to determine population structure in small planktivorous alcids, with panmixia in highly mobile species, clear population differentiation in resident species and intermediate population differentiation in more dispersive species.

Avian Predation in a Declining Outbreak Population of the Spruce Budworm, Choristoneura fumiferana (Lepidoptera: Tortricidae).

Simple SummaryCages preventing access to birds were used to measure the rate of predation by birds in a spruce budworm population during the decline of an outbreak. Three species of budworm-feeding warblers were involved in this predation on larvae and pupae. It was found that bird predation is a very important source of mortality in declining spruce budworm populations, and that bird foraging behavior changes as budworm prey become rare at the end of the outbreak.The impact of avian predation on a declining population of the spruce budworm, Choristoneura fumifereana (Clem.), was measured using single-tree exclosure cages in a mature stand of balsam fir, Abies balsamea (L.), and white spruce, Picea glauca (Moench.) Voss. Bird population censuses and observations of foraging and nest-feeding activity were also made to determine the response of budworm-linked warblers to decreasing food availability. Seasonal patterns of foraging. as well as foraging success in the declining prey population was compared to similar information from birds observed in another stand where the spruce budworm population was rising. Avian predation was an important source of mortality between the 4th instar and moth emergence in the declining outbreak population. Mortality by predation increased from negligible to over 98% as budworm density dropped from 100 to <1 larva/kg of host foliage, over 3 years. Calculations based on nest-feeding activity and basic metabolic demands support these observed rates. Seasonal and yearly differences in predation rates observed between the two host-tree species correspond to equivalent shifts in bird foraging behavior in response to dropping insect density. In particular, a preference for searching on white spruce disappeared, although budworm-linked birds remained more efficient at finding food on this plant. The ability to change foraging behavior as prey density dropped differed between bird species.

Pairing automated mark-recapture and social network models to explore the effects of landscape configuration on hummingbird foraging patterns.

Landscape changes can alter pollinator movement and foraging patterns which can in turn influence the demographic processes of plant populations. We leveraged social network models and four fixed arrays of five hummingbird feeders equipped with radio frequency identification (RFID) data loggers to study rufous hummingbird (Selasphorus rufus) foraging patterns in a heterogeneous landscape. Using a space-for-time approach, we asked whether forest encroachment on alpine meadows could restrict hummingbird foraging movements and impede resource discovery. We fit social network models to data on 2221 movements between feeders made by 29 hummingbirds. Movements were made primarily by females, likely due to male territoriality and early migration dates. Distance was the driving factor in determining the rate of movements among feeders. The posterior mean effects of forest landscape variables (local canopy cover and intervening forest cover) were negative, but with considerable uncertainty. Finally, we found strong reciprocity in hummingbird movements, indicative of frequent out and back movements between resources. Together, these findings suggest that reciprocal movements by female hummingbirds could help maintain bidirectional gene flow among nearby subpopulations of ornithophilous plants; however, if the distance among meadows increases with further forest encroachment, this may limit foraging among progressively isolated meadows.

Survival of the fattest: linking body condition to prey availability and survivorship of killer whales

AbstractRecovering small, endangered populations is challenging, especially if the drivers of declines are not well understood. While infrequent births and deaths may be important to the outlook of endangered populations, small sample sizes confound studies seeking the mechanisms underlying demographic fluctuations. Individual metrics of health, such as nutritive condition, can provide a rich data source on population status and may translate into population trends. We examined interannual changes in body condition metrics of endangered Southern Resident killer whales (SRKW) collected using helicopters and remotely operated drones. We imaged and measured the condition of the majority of all three social pods (J, K, and L) in each of seven years between 2008 and 2019. We used Bayesian multi‐state transition models to identify relationships between body condition changes and both tributary‐specific and area‐based indices of Chinook salmon abundance, and K‐fold cross‐validation to compare the predictive power of candidate salmon covariates. We found that Fraser River (tributary‐specific) and Salish Sea (area‐based) Chinook salmon abundances had the greatest predictive power for J Pod body condition changes, as well as the strongest relationships between any salmon covariates and SRKW condition across pods. Puget Sound (tributary‐specific) Chinook salmon abundance had the greatest predictive power for L Pod body condition changes, but a weaker relationship than Fraser River or Salish Sea abundance had with J Pod body condition. The best‐fit model for K Pod included no Chinook covariates. In addition, we found elevated mortality probabilities in SRKW exhibiting poor body condition (reflecting depleted fat reserves), 2–3 times higher than whales in more robust condition. Collectively, these findings demonstrate that (1) fluctuations in SRKW body condition can in some cases be linked to Chinook salmon abundance; (2) the three SRKW pods appear to have distinct patterns of body condition fluctuations, suggesting different foraging patterns; and (3) aerial photogrammetry is a useful early‐warning system that can identify SRKW at higher risk of mortality in the near future.

Foraging Behaviour of Heterotrigona itama (Apidae: Meliponini) in Residential Areas

This study aims to investigate the foraging behaviour of Heterotrigona itama in exploiting food resources at a residential area, and the viability of this species to adapt to urban microclimatic conditions. Heterotrigona itama prefers to forage at areas closer to their nesting site, where diverse food sources are found. The marked bees of H. itama prefer to forage on various resources available at a 500-metre radius from the house yard. The obtained results indicate that the active foraging pattern of H. itama is negatively correlated to the time phases of a day (p &lt; 0.05). This phenomenon was contributed by the three peaks of foraging hours, which reached a peak in the early morning (6:30 to 8:00 a.m.), moderately peaked towards the evening (2:30 to 3:30 p.m.), and was greatest towards the afternoon (10:30 a.m. to 12:00 p.m.). The ambient temperature and relative humidity were not the primary factors influencing the average number of foragers exiting from and returning to the hives (temperature, p &gt; 0.05; and humidity, p &gt; 0.05). There was a difference between the varieties of content resources collected by the bees (p &lt; 0.05). The nectar or water sources was the highest material (51.39%) that was brought back to the hive by foragers, followed by resin (34.73%) and pollen (13.87%). There was a significant difference in foraging time phases by returning foragers for collecting resin (p &lt; 0.05) and nectar or water (p &lt; 0.02), but there was no significant difference in foraging time phases found for pollen (p &gt; 0.05). We concluded from the results that H. itama is able to withstand urban microclimate conditions, and successfully incorporated pollen, nectar or water, and resin obtained from floral and non-floral resources into their diet.

Immature wild orangutans acquire relevant ecological knowledge through sex-specific attentional biases during social learning.

As a part of growing up, immature orangutans must acquire vast repertoires of skills and knowledge, a process that takes several years of observational social learning and subsequent practice. Adult female and male orangutans show behavioral differences including sex-specific foraging patterns and male-biased dispersal. We investigated how these differing life trajectories affect social interest and emerging ecological knowledge in immatures. We analyzed 15 years of detailed observational data on social learning, associations, and diet repertoires of 50 immatures (16 females and 34 males), from 2 orangutan populations. Specific to the feeding context, we found sex differences in the development of social interest: Throughout the dependency period, immature females direct most of their social attention at their mothers, whereas immature males show an increasing attentional preference for individuals other than their mothers. When attending to non-mother individuals, males show a significant bias toward immigrant individuals and a trend for a bias toward adult males. In contrast, females preferentially attend to neighboring residents. Accordingly, by the end of the dependency period, immature females show a larger dietary overlap with their mothers than do immature males. These results suggest that immature orangutans show attentional biases through which they learn from individuals with the most relevant ecological knowledge. Diversifying their skills and knowledge likely helps males when they move to a new area. In sum, our findings underline the importance of fine-grained social inputs for the acquisition of ecological knowledge and skills in orangutans and likely in other apes as well.

The Predation Game: Does dividing attention affect patterns of human foraging?

Attention is known to play an important role in shaping the behaviour of both human and animal foragers. Here, in three experiments, we built on previous interactive tasks to create an online foraging game for studying divided attention in human participants exposed to the (simulated) risk of predation. Participants used a “sheep” icon to collect items from different target categories randomly distributed across the display. Each trial also contained “wolf” objects, whose movement was inspired by classic studies of multiple object tracking. When participants needed to physically avoid the wolves, foraging patterns changed, with an increased tendency to switch between target categories and a decreased ability to prioritise high reward targets, relative to participants who could safely ignore them. However, when the wolves became dangerous by periodically changing form (briefly having big eyes) instead of by approaching the sheep, foraging patterns were unaffected. Spatial disruption caused by the need to rapidly shift position—rather the cost of reallocating attention—therefore appears to influence foraging in this context. These results thus confirm that participants can efficiently alternate between target selection and tracking moving objects, replicating earlier single-target search findings. Future studies may need to increase the perceived risk or potential costs associated with simulated danger, in order to elicit the extended run behaviour predicted by animal models of foraging, but absent in the current data.

Asymmetric foraging lowers the trophic level and omnivory in natural food webs.

Food webs capture the trophic relationships and energy fluxes between species, which has fundamental impacts on ecosystem functioning and stability. Within a food web, the energy flux distribution between a predator and its prey species is shaped by food quantity-quality trade-offs and the contiguity of foraging. But the distribution of energy fluxes among prey species as well as its drivers and implications remain unclear. Here we used 157 aquatic food webs, which contain explicit energy flux information, to examine whether a predator's foraging is asymmetric and biased towards lower or higher trophic levels, and how these patterns may change with trophic level. We also evaluate how traditional topology-based approaches may over- or under-estimate a predator's trophic level and omnivory by ignoring the asymmetric foraging patterns. Our results demonstrated the prevalence of asymmetric foraging in natural aquatic food webs. Although predators prefer prey at higher trophic levels with potentially higher food quality, they obtain their energy mostly from lower trophic levels with a higher food quantity. Both tendencies, that is, stronger feeding preference for prey at higher trophic levels and stronger energetic reliance on prey at lower trophic levels are alleviated for predators at higher trophic levels. The asymmetric foraging lowers trophic levels and omnivory at both species and food web levels, compared to estimates from traditional topology-based approaches. Such overestimations by topology-based approaches are most pronounced for predators at lower trophic levels and communities with higher number of trophic species. Our study highlights the importance of energy flux information in understanding the foraging behaviour of predators as well as the structural complexity of natural food webs. The increasing availability of flux-based food web data will thus provide new opportunities to reconcile food web structure, functioning and stability.

Characterizing primate home‐ranges in Amazonia: Using ferns and lycophytes as indicators of site quality

AbstractThe habitats present in research sites across Amazonia have usually been characterized only very broadly, for example, as inundated or non‐inundated (terra firma) forests. However, within each of these categories there is considerable variation in soil properties and floristic composition. This variation is likely to determine habitat quality for animal populations through its effects on primary productivity and food availability, thereby affecting carrying capacity. Therefore, comparison of edaphic properties across sites could provide new insight into which factors affect animal foraging patterns, population densities, and home‐range sizes. We provide an example from Estación Biológica Quebrada Blanco in Peruvian Amazonia, where behavioral studies on primates (especially tamarins) have been conducted for more than three decades but little is known about the edaphic or floristic characteristics of the forest they occupy. We used indicator plant species to estimate and map soil base cation concentration and its variability at Estación Biológica Quebrada Blanco. We found that soils in the study area are relatively cation‐poor in a western Amazonian context, which probably translates into low primary productivity. Some differences in soils among the home‐ranges of three tamarin groups were also observed, illustrating the usefulness of the method for detailed habitat mapping.Abstract in Spanish is available with online material.

Temporal and spatial foraging patterns of three Asian honey bee species in Bangalore, India

Honey bees (genus Apis) are important pollinators in Asian tropical agricultural and natural ecosystems, yet the Asian species remain vastly understudied compared to the European honey bee, Apis mellifera. We studied the temporal and spatial foraging patterns of three co-occurring Asian honey bee species in Bangalore, India, to gain a better understanding of how they coexist. We found evidence for temporal resource partitioning, with Apis cerana having activity peaks in the early mornings, Apis florea initiating foraging later in the day, and Apis dorsata having the potential to do much of its foraging activity at night, even when the moon is not yet up. Apart from the established species differences in foraging ranges, we found limited evidence of spatial partitioning of the landscape. Although individual colonies foraging in parallel often focused their foraging effort on different patches, all three species preferred foraging in cultivated garden areas to seminatural or urban areas. These observations add to the growing evidence for a key role of gardens as foraging habitat for bees in cities.

Grazing behaviour and forage selection pattern of heifers in the range

The grazing behaviour of eight yearling white Fulani heifers was studied in two season of year in the south western zone of Nigeria. Time spent on different activities such as drinking, walking, grazing, resting and ruminating were determined using direct eye observation technique. The types of forage selected in both seasons were identified. Visual observations revealed that behaviour was influenced by seasons. The heifers spent 2, 8, 15, 14 and 62% of their time drinking, ruminating, resting, walking and grazing respectively as overall percentage for the two seasons. The forage selection pattern revealed that forbs were mostly selected in the late dry season and grasses in the early rain season. The forages selected in the late dry season were Panicum maximum, Cynodon dactylon, Ipomea aquatical, Leucaena leucocephela, Centrosema mole and Althernanthera dentata. In the early rain season forages selected include Setaria bartata, Echinochloa stagirina, Pennisetum purpureum and Panicum maximum regrowth. It is therefore concluded that the study provides a quick insight into behavioural and forage selection pattern of heifers. Therefore the study can be used to assess grazing animal nutrition condition.

A Change in Foraging Preference of Honey Bees and Plant Diversity during the Last Decade: A Case Study from Lucknow City, India

The expansion of cities around its rural suburbs in recent years is changing the landscape very fast due to human activities planned for their benefit in varied ways. The economically important plants and agri-pharmacoculture have been in focus during recent years. Two decades back the study area (Chinhat, Lucknow city extension, India) was an open, marshy land with a large perennial ox-bow lake (Kathauta tal) of the river Gomti which now flows through the middle of Lucknow city. During the last decade, this extensive agricultural land has changed to a posh urban set-up. The honey samples were collected from beehive in Amity Institute campus and in adjoining areas of Kathauta tal, Chinhat to unravel the foraging pattern of honey bees with the help of its pollen content illustrating the plant resources in the vicinity and for evaluating its forensic application. The pollen spectra of honey reveals more than 50 plant taxa accounting to 60% of trees and the honey produced here is multifloral type. An agri-pharmaco industry was explored in the area with high percentage of Cichorum intybus and Tinospora cordifolia pollen in honey samples. We discuss here the potentials of melissopalynology as a quick, low-cost and highly reliable technique in understanding the pattern of reforestation and reclamation in urban areas, honey quality and its applicability in monitoring the activities of urban human.

Diet of Mass-Stranded Striped Dolphins (Stenella coeruleoalba) in Southern Japan (East China Sea)

Striped dolphins (Stenella coeruleoalba) mass-stranded on 26 April 2013 at Minamisatsuma, Kagoshima Prefecture, in southern Japan (East China Sea). The diet of the mass-stranded striped dolphins was investigated to reveal their foraging pattern through analyses of the stomach contents and stable isotopes in muscle. Of 26 stomachs sampled, 25 contained hard parts of prey animals; no fleshy remains were found in any of the stomachs. The identified prey species represented four cephalopod families: Loliginidae, Onychoteuthidae, Histioteuthidae, and Ommastrephidae. Among these, ommastrephids had the highest abundance (42.4%) and frequency of occurrence (69.2%). A chi-square test revealed that the prey species consumed did not significantly differ between male and female dolphins, although deeper-water squids (Onychoteuthidae and Histioteuthidae) appeared only in the stomachs of females. The values of δ13C ranged from –20.4 to –17.0‰ (mean ± SD: –18.2 ± 0.9‰), and values of δ15N ranged from 10.2 to 12.5‰ (10.8 ± 0.5‰), with a significant difference in δ15N between sexes (P < 0.05).

Patterns of urban foraging in Bengaluru city

Urban foraging is widely prevalent globally, and can provide foragers benefits like additional income and nutritional supplements. However, urban foraging is largely understudied and we have little information on types of species foraged, patterns of foraging, socio-economic profile of foragers, and impact of urbanization on foraging. In this study, we aimed to identify patterns of urban foraging in one of the fastest growing cities in the world, Bengaluru in India. Our specific objectives were to identify a) the foragers b) species foraged and foraging sites c) impact of urbanization on foraging and d) the barriers to foraging. We collected our information through semi-structured interviews with residents from four sites selected across a gradient of urbanization. Sixteen per cent of the respondents reported that they foraged, most of who were women (97 %) belonging to socially (90 %) and economically (81 %) disadvantaged groups. Seventy-six species were foraged across the four sites for food (76 %), medicine (26 %), and cultural practices (18 %). Foraging occurred in unused land (32 %), parks (32 %), farmlands (12 %), native villages (12 %), nearby woodlands (9%) and home gardens (3%). We found significant differences in foragers along a gradient of urbanization (chi square = 34.56, p = 1.5 × 10−7, df = 3) with most foragers at the least urbanized site (40 % of the respondents) and least foragers at the most urbanized site (2% of the respondents). Lack of knowledge of foraged species (66 %) and lack of access (55 %) were the biggest barriers to foraging. Our study demonstrates that foraging occurs in a metropolis like Bengaluru with foragers generally belonging to lower socio-economic backgrounds, who are most vulnerable to changes due to urbanization. Redesigning urban environments to create green spaces for forgeable species to flourish, that are made accessible to marginalized communities, is essential for their nutritional and cultural well-being.

Dynamics of forage and land cover changes in Teltele district of Borana rangelands, southern Ethiopia: using geospatial and field survey data

BackgroundThe gradual conversion of rangelands into other land use types is one of the main challenges affecting the sustainable management of rangelands in Teltele. This study aimed to examine the changes, drivers, trends in land use and land cover (LULC), to determine the link between the Normalized Difference Vegetation Index (NDVI) and forage biomass and the associated impacts of forage biomass production dynamics on the Teltele rangelands in Southern Ethiopia. A Combination of remote sensing data, field interviews, discussion and observations data were used to examine the dynamics of LULC between 1992 and 2019 and forage biomass production.ResultsThe result indicate that there is a marked increase in farm land (35.3%), bare land (13.8%) and shrub land (4.8%), while the reduction found in grass land (54.5%), wet land (69.3%) and forest land (10.5%). The larger change in land observed in both grassland and wetland part was observed during the period from 1995–2000 and 2015–2019, this is due to climate change impact (El-Niño) happened in Teltele rangeland during the year 1999 and 2016 respectively. The quantity of forage in different land use/cover types, grass land had the highest average amount of forage biomass of 2092.3 kg/ha, followed by wetland with 1231 kg/ha, forest land with 1191.3 kg/ha, shrub land with 180 kg/ha, agricultural land with 139.5 kg/ha and bare land with 58.1 kg/ha.ConclusionsThe significant linkage observed between NDVI and LULC change types (when a high NDVI value, the LULC changes also shows positive value or an increasing trend). In addition, NDVI value directly related to the greenness status of vegetation occurred on each LULC change types and its value directly linkage forage biomass production pattern with grassland land use types. 64.8% (grass land), 43.3% (agricultural land), 75.1% (forest land), 50.6% (shrub land), 80.5% (bare land) and 75.5% (wet land) more or higher dry biomass production in the wet season compared to the dry season.

Notes on the diet and foraging habits of the Giant Barred Frog Mixophyes iteratus

ABSTRACT Australian anurans generally display little prey specialisation. Most data available of frog diet is limited to stomach content and faecal analysis with few direct observations of prey capture. Limited information is available on the diet of adult Giant Barred Frogs Mixophyes iteratus. In this paper I report on several observations of M. iteratus feeding on a variety of prey from various taxa. These observations suggest that M. iteratus are opportunistic, ambush predators with a broad diet. Their morphology and hunting behaviour align with existing models of amphibian foraging patterns.

Developed Optimization Algorithms Based on Natural Taxis Behavior of Bacteria

Bio-inspired optimization algorithms are capable of resolving a wide variety of challenges in science and technology, including cognitive science. The principles used by the smallest living organisms in the world could be adopted in the decision-based algorithms for artificial intelligence purposes. Bacterial biological functions and behaviors have been the most effective strategies, which have evolved in these single-cell organisms. The bacteria live based on cognitive and social sensing in nature. Using cognitive processing in bacterial populations enables them to perceive the dynamic surrounding ecosystem and explore their environment. Recently, the behavioral pattern of bacterial foraging has been recruited for resolving optimization issues. This paper reviews 22 developed optimization algorithms based on the bacterial life cycle of motile bacteria. The solicitation of these algorithms applies to a wide range of topics, including cognitive analysis, engineering, medicine, and industry. Following a comparison between different algorithms, we summarize the application of the algorithms in these areas. Eventually, some points are suggested for developing and employing the algorithms in future practical applications of cognitive technology.

Switching between Food Patches Suggests a Need to Balance Nutrients while Foraging in Wild Black Howler Monkeys (Alouatta pigra)

Studies of feeding patch choice in primates have traditionally analyzed individual foraging decisions in relation to patterns of social foraging,dominance, and feeding competition. However, information on detailed ecological and nutritional characteristics of the patches also is neededto understand the basis of feeding patch preferences. In particular, recent models of nutritional ecology have stressed the importance of nutrientbalancing as a primary driver of individual foraging decisions. Here we investigated the behavioral and nutritional factors affecting feeding patchchoice in black howler monkeys (Alouatta pigra) during a 15-month field study in Campeche, Mexico. We collected 1300 hours of behavioral dataon 14 focal animals, including full-day follows of one individual/day recording all feeding activities. We carried out nutritional analyses of foodsfrom feeding trees and calculated daily nutrient intake. A total of 690 trees (i.e., patches) were visited throughout the study period. The time spentfeeding and the amount of food consumed differed significantly according to patch type. Individuals consumed more food in mature and immaturefruit patches than in mature leaf, young leaf, and flower patches. Protein intake rates (kJoule/min) were similar in young and mature leaf patches,and higher than in mature fruit, immature fruit, and flower patches, among which the rate was similar. In the majority of the cases (80.3%), thefocal animals left the feeding patch prior to satiation. On those occasions, resource mixing, or moving from one food type to another food type,accounted for 49.4% of the patch leaving events. The fact that black howler monkeys alternated feeding bouts between fruit and leaf patches, aswell as alternating bouts of higher and lower protein intake, suggest that this pattern could be dictated by the need to balance nutrients.

Disentangling the biotic and abiotic drivers of emergent migratory behavior using individual-based models

Understanding the drivers of movement, migration and distribution of individuals is important for insight into how species will respond to changing environmental conditions. Both abiotic and biotic factors are thought to influence migratory behavior, but their relative roles are difficult to disentangle. For migratory marine predators, both temperature and prey availability have been shown to be significant predictors of space use, though often researchers rely on physical proxies due to the lack of data on dynamic prey fields. We generated spatially explicit individual-based movement models to evaluate the relative roles of abiotic (sea surface temperature; SST) and biotic (prey availability) factors in driving blue whale (Balaenoptera musculus) movement decisions and migratory behavior in the eastern North Pacific. Using output from a lower trophic ecosystem model coupled with a regional ocean circulation model, we parameterized a blue whale movement model that explicitly incorporates prey fields in addition to physical proxies. A model using both SST and prey data reproduced blue whale foraging behavior including realistic timing of latitudinal migrations. SST- and prey-only population models demonstrated important independent effects of each variable. In particular, the SST-only model revealed that warm temperatures limited krill foraging opportunities but failed to drive seasonal foraging patterns, whereas the prey-only model revealed more realistic seasonal and interannual differences in foraging behavior. Our individual-based movement model helps elucidate the mechanisms underlying migration and demonstrates how fine-scale individual decision-making can lead to emergent migratory behavior at the population level. Moreover, determining the relative effects of the physical environment and prey availability on the movement decisions of threatened species is critical to understand how they may respond to changing ocean conditions.