Prey Biomass Research Articles

Prey composition and correlation between morphometry and prey biomass weight of the endemic Nepenthes bicalcarata in Kalimantan, Indonesia

Abstract. Setiawan H, Hakim L, Fernandes AAR, Retnaningdyah C. 2022. Prey composition and correlation between morphometry and prey biomass weight of the endemic Nepenthes bicalcarata in Kalimantan, Indonesia. Biodiversitas 23: 5453-5460. Nepenthes bicalcarata Hook.f. is an endemic plant of the north-western part of Borneo, which is threatened by the conversion of its habitat. The understanding of the ecology of N. bicalcarata in regard to its prey is limited. This research aims to analyze the prey composition of N. bicalcarata and to investigate the correlation between pitcher morphometry and prey biomass weight. This research was done from November 2021 to March 2022 in a peat swamp primary forest in Sintang District, West Kalimantan Province, Indonesia. We used a quantitative descriptive approach and exploration method to gather data from N. bicalcarata in-situ habitat. The morphometry data of N. bicalcarata pitchers were collected in the field while the biomass trapped in N. bicalcarata pitcher liquid was sampled with a plastic bag and preserved with 70% of alcohol. Seven upper pitchers and 39 lower pitchers were recorded in this research. The composition of N. bicalcarata preys was dominated by Formicidae family including C. schmitzi, Polyrhachis sp. and Crematogaster sp.. Besides that, there were also mosquito larvae, ladybugs larvae, Ceratopogonidae larvae and some unidentified flying arthropods as the prey of N. bicalcarata. We found the plant’s parts in the lower pitchers of N. bicalcarata in the peat swamp forest, suggesting a possible mechanism of this plant to extract plant’s parts as alternative nutrient sources, yet this needs further research and intensive field observation. The correlation between pitcher volume and prey biomass weight was significant with P-value =0.00 (<0.01) and regression is formulated as Y (prey weight) = -0.1727 + 0.0039X (pitcher volume). This means that any increase in N. bicalcarata’s pitcher volume will increase the weight of the biomass linearly.

Prey composition and correlation between morphometry and prey biomass weight of the endemic Nepenthes bicalcarata in Kalimantan, Indonesia

Abstract. Setiawan H, Hakim L, Fernandes AAR, Retnaningdyah C. 2022. Prey composition and correlation between morphometry and prey biomass weight of the endemic Nepenthes bicalcarata in Kalimantan, Indonesia. Biodiversitas 23: 5453-5460. Nepenthes bicalcarata Hook.f. is an endemic plant of the north-western part of Borneo, which is threatened by the conversion of its habitat. The understanding of the ecology of N. bicalcarata in regard to its prey is limited. This research aims to analyze the prey composition of N. bicalcarata and to investigate the correlation between pitcher morphometry and prey biomass weight. This research was done from November 2021 to March 2022 in a peat swamp primary forest in Sintang District, West Kalimantan Province, Indonesia. We used a quantitative descriptive approach and exploration method to gather data from N. bicalcarata in-situ habitat. The morphometry data of N. bicalcarata pitchers were collected in the field while the biomass trapped in N. bicalcarata pitcher liquid was sampled with a plastic bag and preserved with 70% of alcohol. Seven upper pitchers and 39 lower pitchers were recorded in this research. The composition of N. bicalcarata preys was dominated by Formicidae family including C. schmitzi, Polyrhachis sp. and Crematogaster sp.. Besides that, there were also mosquito larvae, ladybugs larvae, Ceratopogonidae larvae and some unidentified flying arthropods as the prey of N. bicalcarata. We found the plant’s parts in the lower pitchers of N. bicalcarata in the peat swamp forest, suggesting a possible mechanism of this plant to extract plant’s parts as alternative nutrient sources, yet this needs further research and intensive field observation. The correlation between pitcher volume and prey biomass weight was significant with P-value =0.00 (<0.01) and regression is formulated as Y (prey weight) = -0.1727 + 0.0039X (pitcher volume). This means that any increase in N. bicalcarata’s pitcher volume will increase the weight of the biomass linearly.

Leopard (Panthera pardus) Food Habits in Shared Landscapes: A Case Study of Two Watersheds

Leopard ( Panthera pardus ) food habits was investigated in the human-used landscape of Dabka and Khulgarh Watershed areas of Kumoan Himalayan, Uttarakhan, India between September 2007 and June 2009. In total, 91 and 118 leopard scats were collected from Dabka and Khulgarh respectively. Prey items were identified using non-digested material isolated from scats, as well as a reference collection of hairs and bones from potential prey. Faecal analysis revealed that leopards preyed on 11 and 12 species in Dabka and Khulgarh, respectively. Total diet diversity of leopard was 2.98 in Dabka and 3.00 in Khulgarh. Sambar (53.41%) in Dabka and domestic dog (36.23%) in Khulgarh constituted the bulk of leopards diet both in terms relative prey biomass consumed. Comparison of the observed and expected frequency of occurrence of prey species in leopard diet rejected the hypothesis of non-selective predation in both the study sites. This study showed the survival strategies of leopard by switching diet according to the prey composition of the study area indicating that leopard can survive anywhere. The study highlights the wide dietary width of leopards identified in other research but rarely investigated in shared spaces. Such studies are crucial to the successfull management of "potentially harmful" wildlife in human-use areas. In particular, our result suggest that there is no single key for the existence of the leopard, which should rather depend upon on ecological features of the study area for example, abundance, prey composition, habitat condition and human settlement.

Food Habits of Tiger (Panthera tigris) in Reserve Forest of Uttarakhand, India

Food availability and utilization are among the most critical factors influencing the distribution of free-ranging animals. Little is known about the feeding habit of the tiger ( Panther tigris ) outside the tiger reserves. We collected data on the diet ecology of the tiger in the reserve forest of Kumaon Himalayas, Uttarakhand, India. Scats analysis was used to determine the food habit of the tiger. A total of 55 scats were collected and analyzed. The overall diet diversity of tigers in DWA (Shannon-Wiener Index H') was 2.923. Scat contents were analyzed in terms of both the relative frequency of occurrence and the relative prey biomass consumed. A minimum of 13 different prey species were identified, of which chital constituted 30.91% of the diet followed by sambar (21.82%). The wild prey constituted 77.36% of the diet, whereas domestic prey constituted 23.64% of the diet. Prey selectivity analysis indicated that selective predation by tigers was directed towards prey species with large body mass. This highlights the importance of adjacent forests around protected areas that helps large carnivores to disperse spatially and temporally during resource crunch, competition, and dispersal.

Food habit of Tiger (Panthera tigris) in Tropical Moist Deciduous Forest of Dudhwa National Park, Uttar Pradesh, India

Tiger ( Panthera tigris ) is an endangered felid on the IUCN list. Habitat loss, landscape fragmentation, prey depletion, and poaching have contributed to the decline of the tiger in its entire range in Asia. In India also, it survives only in well-protected tiger reserves and gone or decreased drastically in less-protected areas. The same situation is seen in the terai arc landscape. Thus, accurate knowledge of a species' diet is essential for effective conservation and is vital for conservation initiatives like habitat prioritization, protection, and restoration. Scats analysis was used to determine the food habit of tigers in the tropical moist-evergreen forest of Dudhwa National Park, northern India. A total of 116 scats were collected and analyzed. Scat contents were analyzed in terms of the relative frequency of occurrence and the relative prey biomass consumed. A minimum of 14 prey species were identified. In terms of frequency of occurrence and biomass, the most important prey species were barasingha ( Rucervus duvaucelii) and spotted deer ( Axis axis ), making up to 55% of biomass consumed. Domestic livestock contributed almost 10% to the diet of the tiger. The study revealed that tiger and leopard ( Panthera pardus ), the two main predators in Dudhwa Tiger Reserve, differentiate their niches by segregating the available resources as 55% of the tiger diet comprises barasingha and spotted deer. On the other side, leopard mainly feeds on spotted deer and rodents and may avoid direct competition from the tiger by shifting the space and diet, as revealed by another study in the same area.

Food habit of Tiger (Panthera tigris) in Tropical Moist Deciduous Forest of Dudhwa National Park, Uttar Pradesh, India

Tiger ( Panthera tigris ) is an endangered felid on the IUCN list. Habitat loss, landscape fragmentation, prey depletion, and poaching have contributed to the decline of the tiger in its entire range in Asia. In India also, it survives only in well-protected tiger reserves and gone or decreased drastically in less-protected areas. The same situation is seen in the terai arc landscape. Thus, accurate knowledge of a species' diet is essential for effective conservation and is vital for conservation initiatives like habitat prioritization, protection, and restoration. Scats analysis was used to determine the food habit of tigers in the tropical moist-evergreen forest of Dudhwa National Park, northern India. A total of 116 scats were collected and analyzed. Scat contents were analyzed in terms of the relative frequency of occurrence and the relative prey biomass consumed. A minimum of 14 prey species were identified. In terms of frequency of occurrence and biomass, the most important prey species were barasingha ( Rucervus duvaucelii) and spotted deer ( Axis axis ), making up to 55% of biomass consumed. Domestic livestock contributed almost 10% to the diet of the tiger. The study revealed that tiger and leopard ( Panthera pardus ), the two main predators in Dudhwa Tiger Reserve, differentiate their niches by segregating the available resources as 55% of the tiger diet comprises barasingha and spotted deer. On the other side, leopard mainly feeds on spotted deer and rodents and may avoid direct competition from the tiger by shifting the space and diet, as revealed by another study in the same area.

Leopard (Panthera pardus) Food Habits in Shared Landscapes: A Case Study of Two Watersheds

Leopard ( Panthera pardus ) food habits was investigated in the human-used landscape of Dabka and Khulgarh Watershed areas of Kumoan Himalayan, Uttarakhan, India between September 2007 and June 2009. In total, 91 and 118 leopard scats were collected from Dabka and Khulgarh respectively. Prey items were identified using non-digested material isolated from scats, as well as a reference collection of hairs and bones from potential prey. Faecal analysis revealed that leopards preyed on 11 and 12 species in Dabka and Khulgarh, respectively. Total diet diversity of leopard was 2.98 in Dabka and 3.00 in Khulgarh. Sambar (53.41%) in Dabka and domestic dog (36.23%) in Khulgarh constituted the bulk of leopards diet both in terms relative prey biomass consumed. Comparison of the observed and expected frequency of occurrence of prey species in leopard diet rejected the hypothesis of non-selective predation in both the study sites. This study showed the survival strategies of leopard by switching diet according to the prey composition of the study area indicating that leopard can survive anywhere. The study highlights the wide dietary width of leopards identified in other research but rarely investigated in shared spaces. Such studies are crucial to the successfull management of "potentially harmful" wildlife in human-use areas. In particular, our result suggest that there is no single key for the existence of the leopard, which should rather depend upon on ecological features of the study area for example, abundance, prey composition, habitat condition and human settlement.

Food Habits of Tiger (Panthera tigris) in Reserve Forest of Uttarakhand, India

Food availability and utilization are among the most critical factors influencing the distribution of free-ranging animals. Little is known about the feeding habit of the tiger ( Panther tigris ) outside the tiger reserves. We collected data on the diet ecology of the tiger in the reserve forest of Kumaon Himalayas, Uttarakhand, India. Scats analysis was used to determine the food habit of the tiger. A total of 55 scats were collected and analyzed. The overall diet diversity of tigers in DWA (Shannon-Wiener Index H') was 2.923. Scat contents were analyzed in terms of both the relative frequency of occurrence and the relative prey biomass consumed. A minimum of 13 different prey species were identified, of which chital constituted 30.91% of the diet followed by sambar (21.82%). The wild prey constituted 77.36% of the diet, whereas domestic prey constituted 23.64% of the diet. Prey selectivity analysis indicated that selective predation by tigers was directed towards prey species with large body mass. This highlights the importance of adjacent forests around protected areas that helps large carnivores to disperse spatially and temporally during resource crunch, competition, and dispersal.

Competition between the black‐winged kite and Eurasian kestrel led to population turnover at a subtropical sympatric site

Population expansion of the black‐winged kite Elanus caeruleus has been a global trend in recent decades. Since first recorded in Taiwan in 2001, they rapidly occupied plains areas of this subtropical island which has led to interspecific competition with the wintering Eurasian kestrel Falco tinnunculus. In this study, we analyzed historical surveys to estimate the population trends of both species in Taiwan. We then used Pianka's index to quantify the degree of niche overlap based on diet composition and foraging peaks. Finally, we designed an experiment to test the aggressiveness of the two raptors when facing conspecific or heterospecific intruders. Airport avifauna survey (2002–2017) data from eight different airports and eBird data (2000–2019) from 21 hotspot grids both showed population turnover between the two raptors, with a decline in the wintering Eurasian kestrel and an expansion of the black‐winged kite. Rodents were the largest share of prey for both species, indicating that the two raptors have a high degree of niche overlap (an overlap index of 0.74 by prey frequency, 0.97 by prey biomass and 0.89 by foraging time). The black‐winged kite exhibited higher boldness and aggressiveness toward intruders, with its aggressiveness toward kestrel specimens (2.9 ± 2.4 strikes) significantly higher than that toward kite specimens (1.1 ± 1.8 strikes). Attacks by the black‐winged kite may have prompted the Eurasian kestrel to choose other wintering grounds. As a result, the number of wintering kestrels decreased, leading to opposing population trends of the two species.

A Comparison Study of Predator-Prey Model in Deterministic and Stochastic Environments with the Impacts of Fear and Habitat Complexity.

In theoretical ecology, recent field experiments on terrestrial vertebrates observe that the predator-prey interaction can not only be curtailed by direct consumption but also governed by some indirect effects such as the fear of predator which may reduce the reproduction rate of prey individuals. Based on this fact, we have developed and explored the predator-prey interaction with the influence of both cost and benefit of fear effect (felt by prey). A Holling type III functional response with the effect of habitat complexity has been taken to consume the prey biomass. Positivity and boundedness of the studied system prove that the model is well-behaved. The uniform persistence of the studied system is derived analytically under some parametric restrictions. The feasibility conditions and stability criteria of each equilibrium points have been discussed. Next, we have exhibited the existence of Hopf-bifurcation around the interior equilibrium point. Our mathematical analyses show that habitat complexity and fear effect both have a great impact on the persistence of the predator biomass. Furthermore, we have investigated the effect of breeding delay parameter such that the system loses its stability behaviour and enters into a limit cycle oscillations through Hopf-bifurcation. Numerical simulations are illustrated to verify our analytical outcomes. Numerically, we have perturbed the death rates of prey and predator species with Gaussian white noise terms due to the effects of environmental fluctuations.

Benthic studies adjacent to Sakhalin Island, Russia, 2015 I: benthic biomass and community structure in the nearshore gray whale feeding area

Okhotsk or western gray whales feed in summer along the northeastern coast of Sakhalin Island, Russia, a region with oil and gas extraction facilities. Seismic surveys increased sound levels in the nearshore feeding area in 2015 for part of the summer, potentially displacing whales from preferred foraging habitat or reducing foraging efficiency. Since lost foraging opportunities might lead to vital rate effects on this endangered species, detailed benthic surveys were conducted to characterize benthic community biomass patterns and spatial and temporal differences. Benthic biomass demonstrated strong spatial–temporal interactions indicating that prey biomass differences among locations were dependent on sampling period. Of greatest interest, Amphipoda biomass declined from June to October in the northern and southern portions of the nearshore study area but increased in the middle and Actinopterygii biomass increased in the northern area in mid-summer. Water depth and sediment type were significant covariates with community structure, and water depth strongly covaried with bivalve biomass. Total average prey biomass was ~ 100 g/m2 within the nearshore feeding area with no evidence of reduced biomass among sampling periods or locations, although there were fewer amphipods in the south. Multi-prey investigations provide a stronger basis for inferences than single-prey studies of amphipods when gray whales feed on diverse prey. Benthic community-level variability was moderate to high as would be expected for a shallow-water nearshore area. Overall, spatial and temporal changes in dominant macrofauna biomass reflected small to medium-sized effects that were well within the natural boundaries expected for benthic communities.

Food web ecology of Gulf Stream flounder (Citharichthys arctifrons): a continental shelf perspective.

Gulf Stream flounder, Citharichthys arctifrons, are regularly observed in fish diets of the northeast U.S. continental shelf, yet lack commercial value and are often ignored. Similarly, Gulf Stream flounder diets of the Northwest Atlantic have remained largely unexamined, except for a brief period from 1976 to 1980. To better understand their role in the ecosystem, juvenile through adult Gulf Stream flounder were examined both as a predator and prey, and the magnitude of their feeding footprint (removal of prey biomass) was quantified for the northeast U.S. continental shelf. Their stomachs were sampled from 2005 to 2010, with the majority examined in the field macroscopically. Due to large proportions of unidentifiable prey, the effort was expanded in 2011-2012, and all stomachs were processed in the laboratory microscopically. Gulf Stream flounder were consumed by 15 fish, and what they eat (percentage mass and percentage frequency of occurrence) was documented by season, spatial region and year. Highly benthivorous, Gammaridea and Polychaeta dominated the diet in all years, seasons and regions, but Ophiuroidea (brittle stars) were also prominent in Southern New England during the spring. Gulf Stream flounder diets remained consistent across regions and time, with only a few feeding differences between seasons and one region. Relative to the productivity of benthos for this shelf ecosystem, the feeding footprint of Gulf Stream flounder was minor for their predominant benthic prey with a maximum percentage of benthos production eaten of 0.01% m-2 in Southern New England. With an ecosystem perspective, this feeding information offers a foundation for improving fisheries management among shared living marine resources considering benthic habitat and prey availability.

Consistent predator-prey biomass scaling in complex food webs

The ratio of predator-to-prey biomass is a key element of trophic structure that is typically investigated from a food chain perspective, ignoring channels of energy transfer (e.g. omnivory) that may govern community structure. Here, we address this shortcoming by characterising the biomass structure of 141 freshwater, marine and terrestrial food webs, spanning a broad gradient in community biomass. We test whether sub-linear scaling between predator and prey biomass (a potential signal of density-dependent processes) emerges within ecosystem types and across levels of biological organisation. We find a consistent, sub-linear scaling pattern whereby predator biomass scales with the total biomass of their prey with a near ¾-power exponent within food webs - i.e. more prey biomass supports proportionally less predator biomass. Across food webs, a similar sub-linear scaling pattern emerges between total predator biomass and the combined biomass of all prey within a food web. These general patterns in trophic structure are compatible with a systematic form of density dependence that holds among complex feeding interactions across levels of organization, irrespective of ecosystem type.

Collaborative behaviour and coalitions in male jaguars (Panthera onca)—evidence and comparison with other felids

Most large felids are classified as solitary species, with only lions (Panthera leo) and cheetahs (Acinonyx jubatus) exhibiting social, collaborative behaviours. Herein, we present evidence of the formation of male coalitions by jaguars (Panthera onca), based on data from five studies conducted with camera trapping, GPS telemetry, and direct observations in the Venezuelan Llanos and Brazilian Pantanal. Out of 7062 male records obtained with camera traps or visual observations, we detected 105 cases of male-male interactions, of which we classified 18 as aggression, nine as tolerance, 70 as cooperation/coalition, and eight as unidentified. In two studies, two male jaguars formed stable coalitions lasting over 7 years each. In the Llanos, each coalition male paired and mated with several females. For male jaguar coalitions, we documented similar behaviours as recorded earlier in lions or cheetahs, which included patrolling and marking territory together, invading territories of other males, collaborative chasing and killing other jaguars, and sharing prey. However, different from lions or cheetahs, associated male jaguars spent less time together, did not cooperate with females, and did not hunt cooperatively together. Our analysis of literature suggested that male jaguar coalitions were more likely to form when females had small home range size, a proxy of females’ concentration, while in lions, the male group size was directly correlated with the female group size. Similarly, locally concentrated access to females may drive formation of male coalitions in cheetahs. We conclude that high biomass and aggregation of prey are likely drivers of sociality in felids.Significance statementThe division into social and solitary species in large felids has so far seemed unambiguous, with only lions and cheetahs classified as social species, in which male coalitions also occurred. Our data show that, under certain conditions, male coalitions may also form in jaguar populations. Factors that drive formation of male coalitions in lions and cheetahs, but not in other species of large cats, have not been clear until now. Our analyses indicate that in jaguars, lions, and cheetahs, the concentration of females likely plays the most important role. In jaguars, the probability of male coalition occurrence is highest in populations with the smallest mean female home range size (and thus likely high local density of females), while in lions, male group size is most strongly correlated with female group size.

Direct and indirect influences of macrophyte cover on abundance and growth of juvenile Atlantic salmon

Abstract The relationships between macrophytes and the physical and biological characteristics of the environments that aquatic organisms inhabit are complex. Previous studies have shown that the macrophytes, Ranunculus (subgenus Batrachium), which are dominant in lowland chalk streams and widespread across Europe, can enhance juvenile Atlantic salmon abundance and growth to a greater degree than other physical and biological habitat characteristics. However, mechanistic understanding of how this effect might arise requires consideration of the direct and indirect relationships among habitat characteristics that are likely to be influenced by the presence of macrophyte cover. We applied structural equation modelling to data collected during a 2‐year in‐river manipulative experiment in the River Frome (southern England, U.K.) designed to quantify the magnitude and the relative importance of direct and indirect influences of Ranunculus cover and other physical and biological variables, including water velocity, water depth, prey biomass and body size, and abundance of con‐ and hetero‐specifics, on abundance and somatic growth of 0+ salmon. Results indicated a strongly positive direct influence of Ranunculus cover on salmon abundance, as well as positive influences of Ranunculus on velocity heterogeneity and water depth that are indirectly related to decreased salmon abundance. Interestingly, there was no indication of a direct influence of Ranunculus cover on salmon growth, although Ranunculus was indirectly related to increased salmon growth through its positive influence on prey biomass, an effect mediated by velocity heterogeneity and proportion of fast velocities. These findings provide novel mechanistic insights into the key role of Ranunculus in their native lowland rivers to enhance abundance and improve conditions for multiple food web components. Strategies to maintain or enhance naturally occurring Ranunculus in these rivers are therefore likely to return wide ranging ecosystem benefits, including for species of high conservation value, such as salmon. These mechanistic impacts on habitat heterogeneity and ecosystem productivity could generalise to native macrophytes in other river systems, particularly where habitat is dominated by vegetation in the absence of large substrates.

Feeding ecology of the endangered Asiatic wild dogs (Cuon alpinus) across tropical forests of the Central Indian Landscape

Studies on resource utilisation by carnivores are essential as they aid in assessing their role in a community, by unravelling predator–prey relationships. Globally, prey depletion is one of the primary causes of declining Asiatic wild dog (dhole) populations. Therefore, it is essential to examine their diet across their range. Our study presents insights into dhole feeding ecology across multiple sites from the central Indian landscape of Maharashtra, India, for the first time. We conducted scat analysis using a subset of genetically identified scats and collected additional data from kills observed while tracking radio-collared dholes and other known packs from 2 study sites. We analysed 861 scats, and 191 dhole kills to identify species and age class of prey. We estimated the relative contribution of various prey, utilising non-linear biomass models of prey consumption. Overall, wild ungulates like sambar and chital were the principal prey in terms of biomass (sambar 61.08%; chital 19.08%) and number of prey consumed (sambar 39.28%; chital 13.83%). An analysis of kill data also suggested that dholes strongly preferred the two deer species; and differential selection of age classes was observed at the 2 study sites. Our study can potentially help manage and conserve this important population of an endangered carnivore.

Spatio-temporal dynamics of bluefin tuna (Thunnus thynnus) in US waters of the northwest Atlantic

Atlantic bluefin tuna (Thunnus thynnus) are large, highly migratory fish that support important fisheries. Oceanic conditions influence Atlantic bluefin tuna distribution and it has been hypothesized that stock distributions have shifted in recent years. Distributional shifts can affect regional availability and fleet catchability, introducing a potential bias in fisheries dependent data used for indexing population trends. We developed a vector auto-regressive spatio-temporal model (VAST) to estimate changes in bluefin tuna spatial distribution in US waters and created standardized indices of abundance for large (>177 cm) and small size classes (≤ 177 cm) of fish. Local-scale environmental factors (sea surface temperature (SST), ocean depth) and regional-scale drivers (e.g., Atlantic Multidecadal Oscillation (AMO) and prey biomass) of spatial distribution were explored. Results indicated that from 1993 to 2020, spatial distribution of the larger size class was highly variable, but on average, the total estimated area occupied increased by 96 km2/year and the center of gravity shifted 2 km/year north and 3 km/year east. Results were similar for the smaller size class fish with an average increase in area occupied of 71 km2/year. The center of gravity shifted an average of 1 km/year north and 2 km/year east. The primary factor driving the spatial shifts for both large and small fish was local-scale SST. Standardized indices of abundance were produced and incorporated SST as a covariate of local density. In comparison to prior standardization results, spatio-temporal indices demonstrated less inter-annual variability and produced similar overall trends. This study advanced our understanding of bluefin tuna spatial distributions and generated indices of relative abundance in US waters of the Northwest Atlantic that are more robust to spatio-temporal changes in tuna distributions for consideration in future stock assessments.

Sympatric otariids increase trophic segregation in response to warming ocean conditions in Peruvian Humboldt Current System.

Determining trophic habits of predator communities is essential to measure interspecific interactions and response to environmental fluctuations. South American fur seals, Arctocephalus australis (SAFS) and sea lions Otaria byronia (SASL), coexist along the coasts of Peru. Recently, ocean warming events (2014–2017) that can decrease and impoverish prey biomass have occurred in the Peruvian Humboldt Current System. In this context, our aim was to assess the effect of warming events on long-term inter- and intra-specific niche segregation. We collected whisker from SAFS (55 females and 21 males) and SASL (14 females and 22 males) in Punta San Juan, Peru. We used δ13C and δ15N values serially archived in otariid whiskers to construct a monthly time series for 2005–2019. From the same period we used sea level anomaly records to determine shifts in the predominant oceanographic conditions using a change point analysis. Ellipse areas (SIBER) estimated niche width of species-sex groups and their overlap. We detected a shift in the environmental conditions marking two distinct periods (P1: January 2005—October 2013; P2: November 2013—December 2019). Reduction in δ15N in all groups during P2 suggests impoverished baseline values with bottom-up effects, a shift towards consuming lower trophic level prey, or both. Reduced overlap between all groups in P2 lends support of a more redundant assemblage during the colder P1 to a more trophically segregated assemblage during warmer P2. SASL females show the largest variation in response to the warming scenario (P2), reducing both ellipse area and δ15N mean values. Plasticity to adapt to changing environments and feeding on a more available food source without fishing pressure can be more advantageous for female SASL, albeit temporary trophic bottom-up effects. This helps explain larger population size of SASL in Peru, in contrast to the smaller and declining SAFS population.

Does water availability shift dietary preferences of coyotes in the west desert of Utah?

Water is one of the most essential resources on the planet and shapes entire ecosystems. Across the western United States, thousands of artificial water sources have been installed to assist wildlife populations in arid environments. It has been reported that kit foxes (Vulpes macrotis) can live independently of free-drinking water, but coyotes (Canis latrans) would have to more than triple their intake of prey biomass to meet energy requirements. However, previous researchers discovered no change in coyote space use, nor were survival rates of coyotes influenced by the removal of water sources. We predicted coyote diets in the treatment areas (i.e., water removed) would show an increase in leporids, as a source of preformed water after the water removal to compensate for the lack of free water. However, we found no evidence of a dietary shift by coyotes towards large-bodied prey (i.e., leporids) after water sources were removed; occurrence of leporids in the coyote diet decreased after water removal in both the control and treatment areas. Based on this study and previous research in Utah's west desert, coyotes in the Great Basin ecosystem were not influenced by artificial water sources in a spatial, demographic, or dietary capacity.

Quantitative prey species detection in predator guts across multiple trophic levels by mapping unassembled shotgun reads.

Quantifying species trophic interaction strengths is crucial for understanding community dynamics and has significant implications for pest management and species conservation. DNA-based methods to identify species interactions have revolutionized these efforts, but a significant limitation is the poor ability to quantify the strength of trophic interactions, that is the biomass or number of prey consumed. We present an improved pipeline, called Lazaro, to map unassembled shotgun reads to a comprehensive arthropod mitogenome database and show that the number of prey reads detected is quantitatively predicted from the prey biomass consumed, even for indirect predation. Two feeding bioassays were performed: starved coccinellid larvae consuming different numbers of aphids (Prey Quantity bioassay), and starved coccinellid larvae consuming a chrysopid larvae that had consumed aphids (Direct and Indirect Predation bioassay). Prey taxonomic assignment against a mitochondrial genome database had high accuracy (99.8% positive predictive value) and the number of prey reads was directly related to the number of prey consumed and inversely related to the elapsed time since consumption with high significance (r2 = .932, p= 4.92E-6). Aphids were detected up to 6h after direct predation plus 3h after indirect predation (9h in total) and detection was related to the predator-specific decay rates. Lazaro enabled quantitative predictions of prey consumption across multiple trophic levels with high taxonomic resolution while eliminating all false positives, except for a few confirmed contaminants, and may be valuable for characterizing prey consumed by field-sampled predators. Moreover, Lazaro is readily applicable for species diversity determination from any degraded environmental DNA.