Prey Size Research Articles

Feeling for food: Can rostro-mental hair arrays sense hydrodynamic cues for foraging North Atlantic right whales?

North Atlantic right whales (NARWs; Eubalaena glacialis) possess an arrangement of fine hairs on the rostrum and chin that may be used for hydrodynamic sensing during feeding. These hairs occur across mysticete species and are known to possess adequate innervation in the subdermal follicle to support their consideration as sensory hairs (vibrissae). However, the small size of the hair structure with respect to the enormous scale of the animal's body has caused doubts regarding their utility and prompted speculation that the hairs may be vestigial or minimally functional. Here we show that NARW hairs occur in abundance on the leading surface of the head in a unique and characteristic arrangement. We consider the sensory hairs in context of the fluid environment in which this species forages and argue that the size of the hair is scaled to the size of the animal's small planktonic prey, thus suggesting that the hairs play an important role in the sensory ecology of these animals.

Trophic Dynamics and Feeding Ecology of Skipjack Tuna (Katsuwonus pelamis) off Eastern and Western Taiwan.

The skipjack tuna (Katsuwonus pelamis) is a mesopredator fish species with seasonal abundance in waters off Taiwan. Regional ecological and life-history information has been historically lacking for this species. In recent years, stable isotope analysis (SIA) of carbon and nitrogen has been used to assess predator feeding ecology and broader ecosystem trophic dynamics. This study evaluated comparative skipjack feeding ecology in distinct regions off Taiwan, combining traditional stomach content analysis with SIA of individuals off western (n = 43; 2020) and eastern (n = 347; 2012–2014 and n = 167; 2020) Taiwan. The stomach content analysis showed the most important prey to be ponyfish (Photopectoralis bindus) in western Taiwan and epipelagic squids (Myopsina spp.) and carangids (Decapterus macrosoma;) in eastern Taiwan from 2012 to 2014 and epipelagic carangids (Decapterus spp.) and flying fishes (Cheilopogon spp.) in eastern Taiwan in 2020, suggesting that the skipjack tuna is a generalist predator across regions. In contrast, time-integrated diet estimates from Bayesian mixing models indicated the importance of cephalopods and crustaceans as prey, potentially demonstrating more mesopelagic feeding in less productive waters during skipjack migrations outside the study regions. Skipjack off western Taiwan had a slightly higher estimated trophic position than in the waters off eastern Taiwan, potentially driven by the varying nutrient-driven pelagic food web structures. Skipjack SI values increased with body size off eastern Taiwan but not in western waters, suggesting that opportunistic predation can still result in different predator–prey size dynamics between regions.

Dwarf Mongoose Optimization Algorithm

This paper proposes a new metaheuristic algorithm called dwarf mongoose optimization algorithm (DMO) to solve the classical and CEC 2020 benchmark functions and 12 continuous/discrete engineering optimization problems. The DMO mimics the foraging behavior of the dwarf mongoose. The restrictive mode of prey capture (feeding) has dramatically affected the mongooses’ social behavior and ecological adaptations to compensate for efficient family nutrition. The compensatory behavioral adaptations of the mongoose are prey size, space utilization, group size, and food provisioning. Three social groups of the dwarf mongoose are used in the proposed algorithm, the alpha group, babysitters, and the scout group. The family forage as a unit, and the alpha female initiates foraging, determines the foraging path, the distance covered, and the sleeping mounds. A certain number of the mongoose population (usually a mixture of males and females) serve as the babysitters. They remain with the young until the group returns at midday or evening. The babysitters are exchanged for the first to forage with the group (exploitation phase). The dwarf mongooses do not build a nest for their young; they move them from one sleeping mound to another and do not return to the previously foraged site. The dwarf mongoose has adopted a seminomadic way of life in a territory large enough to support the entire group (exploration phase). The nomadic behavior prevents overexploitation of a particular area. It also ensures exploration of the whole territory because no previously visited sleeping mound is returned. The performance of the proposed DMO algorithm is compared with seven other algorithms to show its effectiveness in terms of different performance metrics and statistics. In most cases, the near-optimal solutions achieved by the DMO are better than the best solutions obtained by the current state-of-the-art algorithms. Matlab codes of DMO are available at https://www.mathworks.com/matlabcentral/fileexchange/105125-dwarf-mongoose-optimization-algorithm.

In natura sit-and-wait behaviour and predation success of a Neotropical dance fly (Diptera: Hybotidae)

ABSTRACT In this study, we provide detailed ethological notes on the predation behaviour of Chvalaea yolkamini Jaume-Schinkel, Soares & Barros, 2020, a neotropical sit-and-wait dance fly from Mexico, with description and video evidence of hunting and feeding behaviours. Furthermore, we analysed in situ predation success in relation to biotic and abiotic factors (prey size, prey taxonomic group, temperature, humidity and perch height). We observed 94 individuals for a total of ~15.68 hours. Chvalaea yolkamini uses its hind legs armed with spikes to strike and handle prey, while its short proboscis pierces and sucks on intersegmental areas as they are less sclerotised. Feeding time ranged from 1.27 to 15.24 minutes. In addition, C. yolkamini was more successful when attacking large-sized prey, but apparently the limit for prey size is the predator’s own size. The individuals were more successful when ambushing large Brachycera than relatively small nematocerous Diptera and Hemiptera. No influence of temperature and humidity was detected, but higher perches favoured predation success. Our study supplies the first detailed information on the perching and hunting behaviour of a sit-and-wait hybotid fly. We advance hypotheses that may be investigated by including covariables, such as wind and prey colouration, with a view to further our comprehension of the sit-and-wait behaviour in predatory animals.

Manipulations of brood age reveal limited parental flexibility in an insectivorous passerine

For birds with altricial nestlings, behavioural flexibility in provisioning may be essential to success, as it enables parents to respond to changes in offspring demand. While parents often increase the quantity of food they provide as nestlings grow, they may also adjust different aspects of this suite of behaviours (i.e. feeding rate, prey type and size and distribution within broods) flexibly in response to nestling age. We tested whether generalist insectivores, mountain bluebirds, Sialia currucoides , respond to abrupt shifts in the body size of nestlings the same way they do when nestlings age normally. During a short-term (within-day) manipulation of nestling age, we recorded provisioning behaviour of parents feeding their own (‘natal’) and an age-manipulated (increased or decreased by 4 days) brood on the same day, in addition to recording provisioning ∼4 days before or after, when natal broods were the same age as manipulated broods. Parents responded to the age manipulation by altering feeding rates, but when broods aged naturally, parents altered the types and sizes of prey they delivered. Parents fed less often and provided larger prey when feeding younger-than-expected broods than when feeding young natal broods. Parents given older-than-expected broods fed more larvae, and fed more often, but provided smaller prey than supplied to older natal broods. Parents feeding older natal broods distributed prey more equitably among nestlings than those feeding either experimental older broods or younger broods (both natural and experimental broods), but this was not due to biased feeding of nestlings according to their body weight. Females fed more often than males and increased the quantity of larvae they provided to younger-than-expected broods. We suggest that parent mountain bluebirds can perceive and respond to both rapid and gradual changes in offspring size, but they may use different cues to adjust feeding rate and prey use. • Provisioning flexibility may allow parents to cope with changes in offspring demand. • Mountain bluebirds typically alter prey type but not feeding rate as nestlings grow. • We briefly manipulated nestling age (± 4 days) to examine parental responses. • During manipulation of brood age, parents altered feeding rate but not prey use. • Parents may adjust feeding rate and prey use in response to different cues.

Size-selective predation by three estuarine zooplanktivorous fish species

Context Zooplanktivorous fish are a key link between abundant zooplankton and higher trophic levels but the foraging behaviour of zooplanktivorous fish is not fully understood. Selective feeding behaviours have been observed, with many species of planktivorous fish targeting certain species and sizes of zooplankton for prey. However, why certain size classes of zooplankton are preferred remains unclear. Aim This study investigated prey selection by three zooplanktivorous fish species through the lens of optimal foraging theory. Methods We assessed the size structure of zooplankton in the environment and compared this with the size distribution of zooplankton in gut contents from three zooplanktivorous fish. Key results The targeted prey size of Atypichthys strigatus and Scorpis lineolata aligns with the prey size classes in the environment that contain the highest overall biomass. Trachurus novaezelandiae showed little evidence of targeting these size classes. Conclusions These prey sizes therefore represent the most efficient prey to target because the return on foraging effort is greatest. By contrast, T. novaezelandiae showed only an underselection of large and small prey. Implications By incorporating this information on this key trophic link between zooplankton and fish, ecosystem models could better resolve the size dependant predation, particularly in size-based models.

At-sea behavioural ecology of the endangered MacGillivray’s prion from Saint Paul Island: combining tracking and stable isotopes

Seabirds play important roles as marine ecosystem sentinels. Studying their at-sea ecology is essential for understanding how environmental variability affects their populations. However, the at-sea ecology of small-sized temperate seabirds remains poorly studied. We explored the at-sea ecology of the Critically Endangered MacGillivray’s prion Pachyptila macgillivrayi breeding on the subtropical Saint Paul Island. Using global location sensor loggers and stable isotope analysis, we investigated movements, migratory strategies, at-sea activity and moulting period, and characterized the isotopic niche of tracked individuals. During incubation, MacGillivray’s prions remained in temperate waters north of the Subtropical Front, possibly feeding on prey caught in cold eddies. During the inter-breeding period, individuals wintered almost equally to the north and south of the Subtropical Front in 2 distinct sectors (Tasman Sea and Southwest Indian Ridge). Daily activity varied seasonally, and individuals overwintering in the Tasman Sea spent more time flying at night when moonlight intensity was high. Moulting occurred after the breeding period and lasted longer compared to other prion species. Isotopic data suggest a higher dietary proportion of low trophic-level prey for MacGillivray’s prions than for Antarctic and slender-billed prions, highlighting trophic segregation in relation to bill width. Our study provides new evidence to understand the suite of adaptations allowing the abundant prion species to coexist by feeding on prey of different sizes. Contrary to the majority of seabird species, MacGillivray’s prions from Saint Paul Island exhibited 2 migratory tactics with associated differences in at-sea activity, leading to questions about the origin of these differences.

Mini DNA barcodes reveal the details of the foraging ecology of the largehead hairtail, Trichiurus lepturus (Scombriformes: Trichiuridae), from São Paulo, Brazil

Abstract The largehead hairtail, Trichiurus lepturus, is an opportunistic, voracious, and piscivorous predator. Studies of fish feeding behavior based on the analysis of stomach contents are limited by the potential for the visual identification of the ingesta. However, molecular tools, in particular DNA barcoding, have been used successfully to identify stomach contents. When morphological analyses are not possible, molecular tools can precisely identify the components of the diet of a fish based on its stomach contents. This study used mini barcoding to identify food items ingested by T. lepturus off the northern coast of São Paulo State, Brazil. Forty-six sequences were obtained and were diagnosed as belonging to six different fish species: Pimelodus maculatus, Paralonchurus brasiliensis, Isopisthus parvipinnis, Opisthonema oglinum, Harengula clupeola, and Pellona harroweri or as belonging to the genera Lycengraulis and Sardinella. Trichiurus lepturus is an opportunistic predator that will exploit an available prey of an appropriate size. The results indicate that these fish migrate to warmer waters, such as those found in estuarine environments, at certain times of the year, where they exploit prey species that reproduce in this environment. One example was Pimelodus maculatus, which was the prey species most exploited based on the analysis of the material collected.

Relationship between fish size and otolith size of four deep-sea fishes from the Western Bay of Bengal, India

The present study provides the otolith morphology and morphometric relationships with fish size of four deep-sea fishes ( Parascombrops pellucidus Alcock, 1889, Alepocephalus blanfordii Alcock, 1892, Lamprogrammus niger Alcock, 1891, Pterygotrigla hemisticta (Temminck & Schlegel, 1843)) collected from western Bay of Bengal during March 2020. Among these, the equations were derived for the first time for three species ( P. pellucidus , A. blanfordii , L. niger ). Sampling was done as a part of deep-sea exploratory survey of FORV Sagar Sampada along the deeper shelf regions of the Bay of Bengal at a depth range of 200 – 1000 m using high-speed demersal trawl (HSDT-CV). The numerical relations established using regression between fish size (TL) and various otolith morphometric measurements (otolith length (OL), otolith height (OH), otolith weight (OWe), otolith area (OA) and otolith perimeter (OP)) can be used to predict the prey size in food and feeding studies for studying the food web dynamics of less-studied deep-sea fishes. LWR of the otolith of selected species showed a negative allometric growth ( t- test, p < 0.5). The higher r 2 value ( > 0.70) obtained for the relationship between fish size (TL) and various otolith morphometric measurements indicates the robustness of the model. The representative images of otoliths of these fishes will be helpful to the taxonomists for the species confirmation and reconstruction of past species assemblages in the palaeontological studies.

Differential clearance rates of microbial phylotypes by four appendicularian species

Appendicularians are abundant planktonic filter feeders that play a significant role in the pelagic food web due to their high clearance rates. Their diet and feeding rates have typically been measured as bulk chlorophyll or cell removal, with some attention given to prey size but no differentiation between the microbial phylotypes. Using a combination ofin situand laboratory incubations with flow cytometry and next-generation sequencing, we found species-specific differences in clearance rates and diet compositions of 4 common species:Oikopleura albicans,O. fusiformis,O. longicauda, andO. dioica. WhileO. albicansmost efficiently removed nano-eukaryotic algae, the other smaller species preferentially removed micron-sized pico-eukaryotic algae. Pico- and nano-eukaryotic cells constituted the major food source of the studied appendicularians despite their occurrence in oligotrophic water dominated by prokaryotic cells. Across species, pico- and nano-planktonic microalgae biomass comprised 45 to 75% of the appendicularian diets. Although non-photosynthetic bacteria were removed at lower rates than all other prey groups, their total contribution to the appendicularian diet was not trivial, representing 5 to 19% of the planktonic carbon in the appendicularian diet; pico-cyanobacteria contributed an additional 9 to 18%. Removal rates and efficiencies of pico-eukaryotes were higher than those of prokaryotes of similar size. Strikingly different clearance rates were observed for different prokaryotic phylotypes, indicating that factors other than size are involved in determining the capturability of the cells. Collectively, our findings provide additional evidence for differential retention of microbial prey among mucous-mesh grazers and its substantial effect on the upper-ocean microbial community.

Influence of different weather aspects on breeding performance, food supply and nest-space use in hoopoe offspring

In this study, we investigated the influence of different weather aspects on breeding performance, food supply and nest-space use in hoopoe offspring (Upupa epops). Camera recordings of 88 nests were used to examine how ambient environmental conditions influence food supply, offspring nest-space use and the trade-off nestlings face regarding the two mainly used locations in the nest. Therefore, we provide a comprehensive analysis involving different factors including weather parameters together with food provisioned to nestlings on different temporal scales to identify the factors having the most influence on nest-space use. We found that different breeding conditions significantly influenced how nestlings used the nest. During excessively humid weather, nestlings spent more time under the entrance hole when small food was delivered. However, nestlings supplied with large prey more often remained hidden in the distant area, despite the adverse weather situation. In all three aspects and temporal scales, our analysis confirmed that prey was the most important factor influencing offspring nest-space use, suggesting a crucial role of large insects for hoopoes. Finally, we found that long-term effects of weather affect overall food provisioned to nestlings and thus offspring behaviour. We provide evidence that parental feeding location and prey size, which are in turn influenced by weather conditions, are the most influential factors for nest-space use. This study expands our knowledge of parent–offspring communication and how environmental factors may lead to differential nest-space use, which may be regarded as the earliest form of habitat preference in birds.Significance statementNests are usually constrained in space but designed to protect offspring from the environment while giving them limited possibilities to express behavioural diversity. This is particularly true for bird nests, where nestlings are usually packed in close contact with one another and without much space for movement, except begging. Here we demonstrate that nest features, such as available nest space together with environmental conditions surrounding a nest, influence nestling strategies and behaviours, including social interactions between nest mates, which further leads to fitness consequences. Our results seem to be of great importance for habitat selection theory in birds, in particular regarding the early development of habitat preferences (imprinting) and use. On the other hand, the result may also have important implications for conservation issues given that nestling behaviour may be used as a determinant of environmental quality.

Predicting prey recovery from scats of California sea lions (Zalophus californianus) for novel prey species and sizes

ABSTRACTDiet studies of marine top predators increasingly inform assessments of prey stocks and ecosystems, as well as predator ecology. Prey hard parts provide quantitative information on diet composition. However, species and size variation in digestion of hard parts, and thus in recovery rates, introduces bias in diet reconstruction. Captive feeding studies estimate species- and size-specific recovery rates of prey hard parts in pinnipeds, but such studies can only include a small subset of prey species and sizes consumed by these commonly generalist predators. We developed a generalized linear mixed effects model that estimates recovery rates of otoliths in California sea lion (Zalophus californianus) scats from otolith morphometrics, based on previously published captive feeding studies. The resulting model explains 85% of the variance in recovery rates among common teleost prey species of California sea lions. We also reestimated cephalopod beak recovery rate in California sea lion scats using an intercept-only mixed effects model. The resulting models can estimate recovery rates—and numerical correction factors—for novel teleost and cephalopod prey species and sizes in California sea lion scats, supporting more accurate reconstruction of diet composition in the wild and suggesting a way forward for other pinniped species.

Prey Status Affects Paralysis Investment in the Ponerine Ant Harpegnathos venator.

Simple SummarySome ants sting their prey to paralyze or kill them when foraging. Some studies have found that paralysis of prey may also be used in food storage. To further understand the foraging behavior of predatory ants and the underlying mechanism, we systematically observed the foraging behavior of Harpegnathos venator when provided with different types of food, different prey sizes, and different prey numbers, and we studied its paralysis behavior in relation to prey under different food supply conditions through controlled experiments. We found that the stings of Harpegnathos venator completely paralyzed the cockroaches. The stinging time was significantly longer at a higher prey activity level and for larger cockroaches. In addition, there was no significant difference in the stinging time of H. venator for different prey densities. It was much shorter for legless cockroaches than for normal cockroaches. The results showed that the longer the stinging time for similar cockroaches, the longer it took for the prey to revive and move. The results are helpful for further understanding the behavioral mechanism underlying prey storage in predatory insects.The paralysis behavior of some ponerine ants when foraging may be important for food storage and colony development. However, how workers invest in paralysis under different prey circumstances is often overlooked. Here, we report the prey-foraging behavior and paralysis behavior of Harpegnathos venator under different food supply conditions. Solitary hunting was the main foraging mode of H. venator, with occasional simple collective hunting. Nymphal cockroaches with high activity were the most attractive to H. venator. In the experiment, we found that the stings of H. venator completely paralyzed the cockroaches. The stinging time was significantly longer at a higher prey activity level and for larger cockroaches. In addition, there was no significant difference in the stinging time of H. venator for different prey densities. The results showed that the longer similar cockroaches were stung, the longer it took for them to revive and move. These results are helpful for further understanding the behavioral mechanism underlying the food storage of live prey by predatory insects.

Benefits and costs of social foraging in velvet worms

AbstractGroup living is ubiquitous in nature, and social foraging is among the common forms of cooperative behaviour in animals. Understanding the evolution and maintenance of social foraging requires knowledge of the underlying benefits and costs to group members, though these are only known for few model taxa, which often lie at the extremes of social organisation. Here, we experimentally examined hypothesised benefits and costs of social foraging in the velvet wormEuperipatoides rowelli; the only Onychophoran currently known to live and forage in groups. To explore benefits, we tested the effects of natural group size and controlled prey size on the latency to attack and begin consuming prey, the likelihood of complete prey consumption and the time taken to completely consume prey. Our focal cost was aggressive intraspecific interactions in the form of biting, kicking and striking, which may present a particular risk to soft‐bodied velvet worms. As predicted, we found a positive scaling of most effects with the size of foraging groups. Larger groups were faster to attack and begin consuming prey, and more likely to completely consume prey, though they took longer to do so. This may be a consequence of the increasing representation of juveniles in larger aggregations. However, larger groups were also subject to heightened aggression among conspecifics, though is it unclear whether such a cost holds at the level of individual group members. Variation in prey size and, hence, resource availability had little effect across all outcomes, except for a slightly reduced likelihood of completely consuming larger prey. A time‐course analysis of individual activity suggested the existence of feeding hierarchies with adults excluding juveniles, particularly when resources are scarce. Taken together, our results offer the first support for the existence of foraging benefits and costs to group membership inE. rowelli, which may contribute to the maintenance of group living in this evolutionary significant taxon.

Early Pleistocene hominin subsistence behaviors in South Africa: Evidence from the hominin-bearing deposit of Cooper's D (Bloubank Valley, South Africa)

Evidence of the consumption of meat through hunting or scavenging by Early Pleistocene hominins is scarce, particularly in South Africa. Moreover, the interpretations of taphonomic evidence are subject to an important discussion commonly called the ‘hunting-vs-scavenging debate.’ Until today, only the Swartkrans Members 1–3 site has yielded a butchered bone assemblage large enough to permit reconstruction of carcass acquisition strategies by Early Pleistocene hominins in South Africa. This leaves an information gap between 1.4 and 1.0 Ma. Here, we provide the first evidence of meat consumption by hominins during this gap, based on the zooarchaeological study of the large mammal bone assemblage recovered from the Cooper's D site, South Africa. Based on skeletal part representation, our results show density-mediated attrition of bovid bones due to predepositional and postdepositional destruction. We argue that this attrition is the result of both abiotic (i.e., decalcification) and biotic (i.e., carnivore ravaging) processes. Bovid mortality profiles point out the involvement of ambush predators such as large felids. Bone surface modifications also indicate that the assemblage has been accumulated mostly by carnivores but with some hominin involvement as well. We observe all the stages of animal carcass processing (skinning, disarticulation, defleshing, marrow extraction) as well as the exploitation of a diversity of prey size classes at both Swartkrans Members 1–3 and Cooper's D. Thus, our study shows the importance of the Cooper's D bone assemblage for understanding Early Pleistocene hominin subsistence behaviors. Moreover, this article highlights the need for including long bone flake specimens in the analysis of large bone assemblages from South African caves to better understand the Early Pleistocene hominin bone damage record.

A Biomimetic Drosera Capensis with Adaptive Decision‐Predation Behavior Based on Multifunctional Sensing and Fast Actuating Capability

AbstractThe sophistication, adaptability, and complexity of biological systems have provided enormous inspiration and have been a continuous source of numerous innovations. Soft living organisms like drosera capensis have amazing predatory behavior that can capture prey of ideal size, enabling them to interact with environmental stimuli efficiently. Mimicking such natural intelligence in artificial systems with systematical functions of multiple information perception, neuronal transmission, and adaptive motility remains a grand challenge. Here, a biomimetic drosera capensis is reported that is capable of multifunctional self‐sensing, automatic regulation, and adaptive actuation in response to diverse stimuli with intelligent predation capability in an entirely closed‐loop fashion. The functional system heterogeneously integrates the thermal‐responsive soft actuator as the muscle‐like motor and flexible tactile, strain, and piezoelectric multimodal sensors as somatosensory receptors. With the synergistic effect of multifunctional sensing and fast actuating schemes, the artificial drosera capensis deconvolutes multiple characteristics of the catching process (e.g., strain rate, magnitude, and direction) and thus holds impressive predatory behavior for ideal‐sized prey. This electronically innervated artificial drosera capensis with multimodal sensing and self‐regulated actuating capability through the closed‐loop control of sensing and actuating system paves the way for the development of adaptive soft robots.

Preliminary analysis on the composition of fish and cephalopod in diet of Dosidicus gigas in the high sea of Eastern Pacific Ocean

Dosidicus gigas is widely distributed in the Eastern Pacific Ocean and plays an important role in the marine ecosystem. In this study, we identified and analyzed 4131 otoliths and 75 beaks from the stomach content residuals of 62 D. gigas samples, which were collected by Chinese squid jigging vessels in the high sea of Eastern Pacific Ocean from June to December 2019. The results showed that the preys of D. gigas included 10 fish species and 4 cephalopod species. Judging from the frequency of appearance and percentage of amount, Vinciguerria lucetia, Diogenichthys laternatus, and Triphoturus mexicanus were the dominant myctophidae prey of D. gigas. Among those preys, V. lucetia was the most important one, as it was found in all D. gigas with different mantle lengths. D. gigas, Sthenoteuthis oualaniensis, and Onychoteuthis banksii were the dominant cephalopod prey. With the growth of mantle length of D. gigas, the number of prey species, the percentage of cephalopod and myctophidae preys, and the size of preys increased, and thus the trophic level of preys increased as the trophic pattern of preys changed. Our results could provide basic information for evaluating the contribution of different preys in the preying transformation of D. gigas.

Environmental factors influencing spotted hyena and lion population biomass across Africa.

The spotted hyena (Crocuta crocuta Erxleben) and the lion (Panthera leo Linnaeus) are two of the most abundant and charismatic large mammalian carnivores in Africa and yet both are experiencing declining populations and significant pressures from environmental change. However, with few exceptions, most studies have focused on influences upon spotted hyena and lion populations within individual sites, rather than synthesizing data from multiple locations. This has impeded the identification of over‐arching trends behind the changing biomass of these large predators. Using partial least squares regression models, influences upon population biomass were therefore investigated, focusing upon prey biomass, temperature, precipitation, and vegetation cover. Additionally, as both species are in competition with one other for food, the influence of competition and evidence of environmental partitioning were assessed. Our results indicate that spotted hyena biomass is more strongly influenced by environmental conditions than lion, with larger hyena populations in areas with warmer winters, cooler summers, less drought, and more semi‐open vegetation cover. Competition was found to have a negligible influence upon spotted hyena and lion populations, and environmental partitioning is suggested, with spotted hyena population biomass greater in areas with more semi‐open vegetation cover. Moreover, spotted hyena is most heavily influenced by the availability of medium‐sized prey biomass, whereas lion is influenced more by large size prey biomass. Given the influences identified upon spotted hyena populations in particular, the results of this study could be used to highlight populations potentially at greatest risk of decline, such as in areas with warming summers and increasingly arid conditions.

Clovis through Big Sandy Technological Response to the Younger Dryas in Northern Alabama

ABSTRACT Kuhn and Miller (2015) suggest that changes in projectile point life histories could result from (a) increased replacement costs due to limited raw material access, or (b) a decline in average hunting returns. In northern Alabama, where raw material access can be held constant, we use variation in biotic structures to make predictions for life histories of Clovis to Big Sandy projectile points over the course of the Younger Dryas (12,900–11,700 calendar years ago). Then, using data from the Alabama Paleo Point Survey and private collections, we find a decrease in projectile point size through time, and fluctuations in resharpening. These trends follow changes in forest structure, average prey size, and hunting returns. We conclude that there are no abrupt technological changes coeval with the Younger Dryas onset. However, with the Younger Dryas terminus and subsequent Holocene warming, foragers in northern Alabama made significant changes in projectile point technology.

Energy-mediated responses to changing prey size and distribution in marine top predator movements and population dynamics.

Climate change is modifying the structure of marine ecosystems, including that of fish communities. Alterations in abiotic and biotic conditions can decrease fish size and change community spatial arrangement, ultimately impacting predator species which rely on these communities. To conserve predators and understand the drivers of observed changes in their population dynamics, we must advance our understanding of how shifting environmental conditions can impact populations by limiting food available to individuals. To investigate the impacts of changing fish size and spatial aggregation on a top predator population, we applied an existing agent-based model parameterized for harbour porpoises Phocoena phocoena which represents animal energetics and movements in high detail. We used this framework to quantify the impacts of shifting prey size and spatial aggregation on porpoise movement, space use, energetics and population dynamics. Simulated individuals were more likely to switch from area-restricted search to transit behaviour with increasing prey size, particularly when starving, due to elevated resource competition. In simulations with highly aggregated prey, higher prey encounter rates counteracted resource competition, resulting in no impacts of prey spatial aggregation on movement behaviour. Reduced energy intake with decreasing prey size and aggregation level caused population decline, with a 15% decrease in fish length resulting in total population collapse Increasing prey consumption rates by 42.8±4.5% could offset population declines; however, this increase was 21.3±12.7% higher than needed to account for changes in total energy availability alone. This suggests that animals in realistic seascapes require additional energy to locate smaller prey which should be considered when assessing the impacts of decreased energy availability. Changes in prey size and aggregation influenced movements and population dynamics of simulated harbour porpoises, revealing that climate-induced changes in prey structure, not only prey abundance, may threaten predator populations. We demonstrate how a population model with realistic animal movements and process-based energetics can be used to investigate population consequences of shifting food availability, such as those mediated by climate change, and provide a mechanistic explanation for how changes in prey structure can impact energetics, behaviour and ultimately viability of predator populations.