Predator Growth Research Articles

Comparative analysis of eco-epidemic model with disease in prey and gestation delay in predator: implications for population dynamics

Gestation is a very significant phenomenon in predator-prey dynamics. It influences the future predation rates and the growth of species. Gestation is the period of development of an embryo or fetus in a female mammal, from conception to birth. It plays a critical role in population dynamics and reproductive strategies in ecological studies. This article presents a comparative study of eco-epidemic models with and without time delay terms. The model takes into account a prey-predator system, dividing the prey population into susceptible and infected compartments. This article incorporates a time delay into the predator growth term to represent gestation delay. This article investigates the impact of time delay as a gestation delay on the model’s dynamics and compares the results with those of the non-delay model. Our analytical and numerical studies reveal that the time delay stabilizes the model, exhibits switching behaviour, and leads to chaotic behaviour through periodic doubling. Moreover, the gestation delay destabilizes the model by causing Hopf bifurcations to emerge at multiple points. Our findings indicate that the delay model has richer dynamics than the non-delay model. The numerical simulations using MATLAB, along with the DDE-biftool and Matcont packages, illustrate the bifurcation analysis, phase portraits, and time series plots for both models. Our findings highlight the significant effects of gestation delay on the dynamics of eco-epidemic models.

Unravelling the Influence of ENSO and SAM Patterns on Skate Growth: The Case of the Shorttail Yellownose Skate in Patagonia, Argentina

ABSTRACTIn recent decades, the growth, physiology and distribution of many elasmobranch species have been altered as a result of environmental changes that affect prey abundance, availability and composition. Consequently, variations in nutrient input during climate events could manifest in the growth of their hard tissues. This study focuses on assessing the impact of the El Niño‐Southern Oscillation (ENSO) and the Southern Annular Mode (SAM) on the growth of Shorttail Yellownose skate (Zearaja brevicaudata) in Patagonia, Argentina. To achieve this, vertebrae from 115 Z. brevicaudata specimens were analysed, and growth rings were dated and measured. By using cubic splines with varying flexibility, we constructed three standard chronologies. Generalized additive models (GAMs), the chronology with the best the R‐bar () and expressed population signal (EPS) were employed and values obtained from them linked to annual time series data of the Multivariate ENSO Index (MEI) and SAM, considering lags in the biological response. Surprisingly, no significant association was found with the MEI time series. However, a noteworthy positive association emerged between the chronology and the SAM time series lagged by 1 year, suggesting that SAM‐related climatic conditions could delay their transfer into the Patagonian marine ecosystem, subsequently impacting the growth of this ectothermic predator.

Predator–prey systems with a variable habitat for predators in advective environments

AbstractCommunity composition in aquatic environments can be shaped by a broad array of factors, encompassing habitat conditions in addition to abiotic conditions and biotic interactions. This paper pertains to reaction–diffusion–advection predator–prey model featuring a variable predator habitat in advective environments, governed by a unidirectional flow. First, we establish the near‐complete global dynamics of the system. In instances where the functional response to predation conforms to Holling‐type I or II, we explore the uniqueness and stability of positive steady‐state solutions via the application of particular auxiliary techniques, the comparison principle for parabolic equations, and perturbation analysis. Furthermore, we obtain the critical positions at the upper and lower boundaries of the predator's habitat, which determine the survival of the prey irrespective of the predator's growth rate. Finally, we show how the location and length of the predator's habitat affect the persistence and extinction of predators and prey in the event of a small population loss rate at the downstream end. From the biological point of view, these results contribute to our deeper understanding of the effects of habitat on aquatic populations and may have applications in aquaculture and the establishment of protection zones for aquatic species.

Sustainable management of predatory fish affected by an Allee effect through marine protected areas and taxation

Ecological balance and stable economic development are crucial for the fishery. This study proposes a predator–prey system for marine communities, where the growth of predators follows the Allee effect and takes into account the rapid fluctuations in resource prices caused by supply and demand. The system predicts the existence of catastrophic equilibrium, which may lead to the extinction of prey, consequently leading to the extinction of predators, but fishing efforts remain high. Marine protected areas are established near fishing areas to avoid such situations. Fish migrate rapidly between these two areas and are only harvested in the nonprotected areas. A three-dimensional simplified model is derived by applying variable aggregation to describe the variation of global variables on a slow time scale. To seek conditions to avoid species extinction and maintain sustainable fishing activities, the existence of positive equilibrium points and their local stability are explored based on the simplified model. Moreover, the long-term impact of establishing marine protected areas and levying taxes based on unit catch on fishery dynamics is studied, and the optimal tax policy is obtained by applying Pontryagin’s maximum principle. The theoretical analysis and numerical examples of this study demonstrate the comprehensive effectiveness of increasing the proportion of marine protected areas and controlling taxes on the sustainable development of fishery.

Range of trait variation in prey determines evolutionary contributions to predator growth rates.

Evolutionary and ecological dynamics can occur on similar timescales and thus influence each other. While it has been shown that the relative contribution of ecological and evolutionary change to population dynamics can vary, it still remains unknown what influences these differences. Here, we test whether prey populations with increased variation in their defense and competitiveness traits will have a stronger impact of evolution for predator growth rates. We controlled trait variation by pairing distinct clonal lineages of the green alga Chlamydomonas reinhardtii with known traits as prey with the rotifer Brachionus calyciforus as predator and compared those results with a mechanistic model matching the empirical system. We measured the impact of evolution (shift in prey clonal frequency) and ecology (shift in prey population density) for predator growth rate and its dependency on trait variation using an approach based on a two-way ANOVA. Our experimental results indicated that higher trait variation, i.e., a greater distance in trait space, increased the relative contribution of prey evolution to predator growth rate over 3-4 predator generations, which was also observed in model simulations spanning longer time periods. In our model, we also observed clone-specific results, where a more competitive undefended prey resulted in a higher evolutionary contribution, independent of the trait distance. Our results suggest that trait combinations and total prey trait variation combine to influence the contribution of evolution to predator population dynamics, and that trait variation can be used to identify and better predict the role of eco-evolutionary dynamics in predator-prey systems.

Complex dynamics in a two species system with Crowley–Martin response function: Role of cooperation, additional food and seasonal perturbations

This research article investigates the interaction between prey and a generalist predator, considering the effect of hunting cooperation. The predator–prey interaction is modeled using a predator dependent functional response, specifically the Crowley–Martin type. System’s dynamics are explored using both analytical and numerical techniques. Feasible equilibria are analyzed, and their local stability is determined. Various bifurcations in the system are explored, and one-and two-parameter bifurcation structures are constructed to unveil complex dynamical behaviors. Our findings reveal that both prey and predator face extinction when the predator growth rate from alternative food sources exceeds certain threshold values. However, prey extinction is driven by the higher levels of hunting cooperation among predators, while the availability of external food sources enhances the system’s stability and persistence. Furthermore, we enhance the model by introducing seasonal perturbations, acknowledging the influence of seasonal variations on ecological parameters. The system exhibits diverse patterns in response to seasonality, contributing to a deeper understanding of the dynamics in predator–prey interactions.

Distinct dynamics and proximity networks of hub proteins at the prey-invading cell pole in a predatory bacterium.

In bacteria, cell poles function as subcellular compartments where proteins localize during specific lifecycle stages, orchestrated by polar "hub" proteins. Whereas most described bacteria inherit an "old" pole from the mother cell and a "new" pole from cell division, generating cell asymmetry at birth, non-binary division poses challenges for establishing cell polarity, particularly for daughter cells inheriting only new poles. We investigated polarity dynamics in the obligate predatory bacterium Bdellovibrio bacteriovorus, proliferating through filamentous growth followed by non-binary division within prey bacteria. Monitoring the subcellular localization of two proteins known as polar hubs in other species, RomR and DivIVA, revealed RomR as an early polarity marker in B. bacteriovorus. RomR already marks the future anterior poles of the progeny during the predator's growth phase, during a precise period closely following the onset of divisome assembly and the end of chromosome segregation. In contrast to RomR's stable unipolar localization in the progeny, DivIVA exhibits a dynamic pole-to-pole localization. This behavior changes shortly before the division of the elongated predator cell, where DivIVA accumulates at all septa and both poles. In vivo protein interaction networks for DivIVA and RomR, mapped through endogenous miniTurbo-based proximity labeling, further underscore their distinct roles in cell polarization and reinforce the importance of the anterior "invasive" cell pole in prey-predator interactions. Our work also emphasizes the precise spatiotemporal order of cellular processes underlying B. bacteriovorus proliferation, offering insights into the subcellular organization of bacteria with filamentous growth and non-binary division.IMPORTANCEIn bacteria, cell poles are crucial areas where "hub" proteins orchestrate lifecycle events through interactions with multiple partners at specific times. While most bacteria exhibit one "old" and one "new" pole, inherited from the previous division event, setting polar identity poses challenges in bacteria with non-binary division. This study explores polar proteins in the predatory bacterium Bdellovibrio bacteriovorus, which undergoes filamentous growth followed by non-binary division inside another bacterium. Our research reveals distinct localization dynamics of the polar proteins RomR and DivIVA, highlighting RomR as an early "hub" marking polar identity in the filamentous mother cell. Using miniTurbo-based proximity labeling, we uncovered their unique protein networks. Overall, our work provides new insights into the cell polarity in non-binary dividing bacteria.

Bifurcation analysis of a discrete Leslie–Gower predator–prey model with slow–fast effect on predator

Understanding and accounting for the slow–fast effect are crucial for accurately modeling and predicting the dynamics of predator–prey models, emphasizing the importance of considering the relative speeds of interacting populations in ecological research. This paper examines a predator–prey interaction to study its complex dynamics due to its slow–fast effect on predator populations. The occurrence and stability of equilibria are analyzed. The stability of positive fixed point is dependent on the slow–fast effect parameter , which must fall within a specific range when the generation gap is larger. The positive fixed point becomes unstable for bigger values of because the growth of predators is faster, resulting in the extinction of all prey. Smaller values of cause the positive fixed point to become unstable since the prey grows more quickly while the predator grows more slowly, ultimately causing the extinction of the predator. Moreover, it is shown that Leslie–Gower model experiences Neimark–Sacker and period‐doubling bifurcations at positive equilibrium point. In order to control bifurcation, hybrid control and feedback control methods are employed. Finally, analytical results are confirmed by numerical examples.

Bazykin’s Predator–Prey Model Includes a Dynamical Analysis of a Caputo Fractional Order Delay Fear and the Effect of the Population-Based Mortality Rate on the Growth of Predators

Bazykin’s Predator–Prey Model Includes a Dynamical Analysis of a Caputo Fractional Order Delay Fear and the Effect of the Population-Based Mortality Rate on the Growth of Predators

Ecological determinants of spotted hyena Crocuta crocuta occupancy in Comoé National Park, Côte d’Ivoire

Knowledge of the large carnivore guild is important in view of a possible lion reintroduction into the Comoé National Park (CNP), northern Côte d’Ivoire. We used camera trapping to assess activity patterns, habitat selection, and ecological factors influencing the occupancy of the spotted hyena Crocuta crocuta. Our results showed that the presence of leopard Panthera pardus, the only current other large carnivore and thus potential competitor, did not influence hyena occupancy. Hyena occupancy was only significantly related to Euclidian distance to nearest water point. Manly’s alpha habitat selection index values show a preference of spotted hyena for shrub savannah (αSa = 0.71), and Pianka’s overlap index showed low spatial competition with leopard (OIJ(PNC) = 0.12). Our findings showed that spotted hyena were mostly nocturnal, and generally active at the same time slots with leopard, leading to a high index of temporal overlap (OIJ(time) = 0.78). The kernel density estimation confirmed that spotted hyenas and leopard shared almost half of their activity patterns (Δ1 = 0.49 and 95% CI = 0.26–0.71). Prey diversity is high in CNP but anthropogenic threats appear to suppress population growth of prey and predators. Conservation efforts should continue to reduce pressures before contemplating a potential lion Panthera leo reintroduction.

Mercury Biogeochemistry and Biomagnification in the Mediterranean Sea: Current Knowledge and Future Prospects in the Context of Climate Change

In the 1970s, the discovery of much higher mercury (Hg) concentrations in Mediterranean fish than in related species of the same size from the Atlantic Ocean raised serious concerns about the possible health effects of neurotoxic monomethylmercury (MMHg) on end consumers. After 50 years, the cycling and fluxes of the different chemical forms of the metal between air, land, and marine environments are still not well defined. However, current knowledge indicates that the anomalous Hg accumulation in Mediterranean organisms is mainly due to the re-mineralization of organic material, which favors the activity of methylating microorganisms and increases MMHg concentrations in low-oxygen waters. The compound is efficiently bio-concentrated by very small phytoplankton cells, which develop in Mediterranean oligotrophic and phosphorous-limited waters and are then transferred to grazing zooplankton. The enhanced bioavailability of MMHg together with the slow growth of organisms and more complex and longer Mediterranean food webs could be responsible for its anomalous accumulation in tuna and other long-lived predatory species. The Mediterranean Sea is a “hotspot” of climate change and has a rich biodiversity, and the increasing temperature, salinity, acidification, and stratification of seawater will likely reduce primary production and change the composition of plankton communities. These changes will likely affect the accumulation of MMHg at lower trophic levels and the biomagnification of its concentrations along the food web; however, changes are difficult to predict. The increased evasion of gaseous elemental mercury (Hg°) from warming surface waters and lower primary productivity could decrease the Hg availability for biotic (and possibly abiotic) methylation processes, but lower oxygen concentrations in deep waters, more complex food webs, and the reduced growth of top predators could increase their MMHg content. Despite uncertainties, in Mediterranean regions historically affected by Hg inputs from anthropogenic and geogenic sources, such as those in the northwestern Mediterranean and the northern Adriatic Sea, rising seawater levels, river flooding, and storms will likely favor the mobilization of Hg and organic matter and will likely maintain high Hg bioaccumulation rates for a long time. Long-term studies will, therefore, be necessary to evaluate the impact of climate change on continental Hg inputs in the Mediterranean basin, on air–sea exchanges, on possible changes in the composition of biotic communities, and on MMHg formation and its biomagnification along food webs. In this context, to safeguard the health of heavy consumers of local seafood, it appears necessary to develop information campaigns, promote initiatives for the consumption of marine organisms at lower trophic levels, and organize large-scale surveys of Hg accumulation in the hair or urine of the most exposed population groups.

Dynamics of a generalist predator–prey system with harvesting and hunting cooperation in deterministic/stochastic environment

In this investigation, we explore a predator–prey system characterized by generalist predators exhibiting cooperative behavior during hunting, subject to nonlinear harvesting rate. Employing a Beverton–Holt type functional response to capture the impact of additional food sources on predator growth, our numerical findings affirm the destabilizing influence of hunting cooperation, excessive predation, and supplementary food sources. Conversely, the system demonstrates stabilization in response to increased prey species growth. We unveil the occurrence of both forward and backward bifurcations in the system due to the predator growth attributed to additional food sources, contingent on the degree of hunting cooperation. To broaden the scope, we extend our proposed model to its stochastic counterpart, introducing environmental white noises. Our numerical results anticipate that higher intensities of white noises lead to fluctuations of greater amplitude, while smaller intensities exhibit a more modest impact. Additionally, we elucidate the dynamics of prey and predator populations through histogram plots. The theoretical and numerical insights derived from this study provide a deeper understanding of the intricate dynamics within predator–prey systems of ecological communities, emphasizing the significance of additional food sources for cooperative predators subject to harvesting in both constant and fluctuating environments.

Feeding behavior of yellowfin tuna around two insular regions of the western Atlantic Ocean.

The yellowfin tuna is a very abundant tropical tuna species in the western equatorial Atlantic Ocean and an important fishery resource for the Brazilian tuna fleet. In this study we performed stable isotope analysis to better understand the spatial trophodynamics and dietary changes in yellowfin tuna around two insular marine protected areas in Brazil. A total of 65 yellowfin tuna specimens measuring between 47 and 138 cm LT (total length) were sampled around the archipelagos of Fernando de Noronha (FNA; n = 34) and Saint Peter and Saint Paul (SPSPA; n = 31) between July 2018 and September 2019. Bayesian mixing models and generalized additive models were used to investigate the contributions of four different prey items (zooplankton, cephalopods, fish larvae, and flying fish) to yellowfin tuna diet in each area and their potential changes in relation to predator growth. The four prey items were found to have different overall contributions between the two studied areas, with zooplankton being the most important prey in FNA, whereas flying fish was the most relevant prey to the species' diet in SPSPA. Significant changes in the species diet by size were also found, with fish smaller than 90 cm (TL) having a more generalist diet and larger animals relying more on consuming larger and more nutritious prey (i.e., flying fish). Our results suggest that these two marine protected areas play an important role in ocean dynamics, providing important and different foraging grounds for the development of this predator species.

Evaluation of Black Soldier Fly Hermetia illucens as Food for Pink-Spotted Lady Beetle Coleomegilla maculata.

The discovery of new and improved factitious and artificial diets is necessary for cost-effective rearing of predatory arthropods. This study evaluated Hermetia illucens black soldier fly (BSF) as a suitable alternative food source for rearing the predatory coccinellid Coleomegilla maculata (Cmac). The hypothesis that BSF larval powder was suitable food to support the growth, development, and reproduction of Cmac was tested in the laboratory. When compared to a standard in-house diet containing brine shrimp egg powder plus Chlorella vulgaris green algae and myristic acid (BSE+CM), the BSF and BSF+CM diets reduced immature growth and development. Immatures successfully reared to teneral adults were smaller when fed BSF or BSF+CM rather than BSE+CM. Combining BSF with a powdered artificial diet (AD), i.e., BSF+AD, did not improve predator growth or development, compared to Cmac reared on BSE+CM. Cmac oviposition responses, i.e., egg clutch production, to BSF vs. BSE+CM or BSF+AD vs. BSE+CM did not differ significantly. In conclusion, BSF has the potential to be food that supports Cmac oviposition behavior. Future research is necessary to discover an ideal mixture of BSF, BSE+CM, or AD that supports Cmac growth, development, and reproduction over multiple generations.

Numerical response of predator to prey: Dynamic interactions and population cycles in Eurasian lynx and roe deer

AbstractThe dynamic interactions between predators and their prey have two fundamental processes: numerical and functional responses. Numerical response is defined as predator growth rate as a function of prey density or both prey and predator densities [dP/dt = f(N, P)]. Functional response is defined as the kill rate by an individual predator being a function of prey density or prey and predator densities combined. Although there are relatively many studies on the functional response in mammalian predators, the numerical response remains poorly documented. We studied the numerical response of Eurasian lynx (Lynx lynx) to various densities of its primary prey species, roe deer (Capreolus capreolus), and to itself (lynx). We exploited an unusual natural situation, spanning three decades where lynx, after a period of absence in central and southern Sweden, during which roe deer populations had grown to high densities, subsequently recolonized region after region, from north to south. We divided the study area into seven regions, with increasing productivity from north to south. We found strong effects of both roe deer density and lynx density on lynx numerical response. Thus, both resources and intraspecific competition for these resources are important to understanding the lynx population dynamic. We built a series of deterministic lynx–roe deer models, and applied them to the seven regions. We found a very good fit between these Lotka–Volterra type models and the data. The deterministic models produced almost cyclic dynamics or dampened cycles in five of the seven regions. Thus, we documented population cycles in this large predator–large herbivore system, which is rarely done. The amplitudes in the dampened cycles decreased toward the south. Thus, the dynamics between lynx and roe deer became more stable with increasing carrying capacity for roe deer, which is related to higher productivity in the environment. This increased stability could be explained by variation in predation risk, where human presence can act as prey refugia, and by a more diverse prey guild that will weaken the direct interaction between lynx and roe deer.

ROLE OF SPACE IN AN ECO-EPIDEMIC PREDATOR-PREY SYSTEM WITH THE EFFECT OF FEAR AND SELECTIVE PREDATION

In ecological systems, the fear of predation risk asserts a privilege to the prey species by restricting their exposure to the potential predators. It also imposes costs by constraining the exploration of optimal resources. Additional foods for predators play a pivotal role in the biological conservation programs. The predators have ability to distinguish between the susceptible and infected prey items, and they avoid the latter ones to reduce their fitness cost. A predator-prey model with disease in prey is investigated in this study with an aim to explore the effects of fear factor, additional foods and selective predation on the ecological systems. We also investigate the spatio-temporal model to incorporate the facts that the prey and predator populations perform active movements in the spatial directions for their biological relevance. Both the temporal and spatio-temporal models are analyzed through noteworthy mathematical as well as numerical techniques. Our simulation results show that the level of fear responsible for the reduction in the birth rate of susceptible prey, rate of disease transmission and the selective feeding behavior of predators have potentials to create instability in the ecosystem. In contrast, the level of fear responsible for reduction in the disease prevalence can restore stability in the ecosystem by killing the persistent oscillations. Our eco-epidemic system exhibits chaotic nature if the growth of predators due to additional food sources is very low. We find that the spatio-temporal model demonstrates different spatial patterns of the prey and predator populations in the ecosystem.

Coexistence of one predator and two prey through rapid evolution in predator’s feeding choice

In this article, we study the coexistence of one predator and two prey with evolutionary effects. To that end, we formulate a three-time-scale model with rapid adaptive in predator’s feeding choice, slow prey growth and superslow predator growth. By using the geometric singular perturbation theory and computing the entry–exit function for multidimensional fast–slow systems, we find that the predator and the two prey coexist in a form of relaxation oscillations between being near the extreme values of feeding choice strategy due to the associated delay of stability loss. It is also found that the predator can coexist with the two prey in the form of an interior equilibrium with a locally optimal feeding choice.

Analysis Dynamics Two Prey of a Predator-Prey Model with Crowley–Martin Response Function

The predator-prey model has been extensively developed in recent research. This research is an applied literature study with a proposed dynamics model using the Crowley–Martin response function, namely the development of the Beddington-DeAngelis response function. The aim of this research is to construct a mathematical model of the predator-prey model, equilibrium analysis and population trajectories analysis. The results showed that the predator-prey model produced seven non-negative equilibrium points, but only one equilibrium point was tested for stability. Stability analysis produces negative eigenvalues indicating fulfillment of the Routh-Hurwitz criteria so that the equilibrium point is locally asymtotically stable. Analysis of the stability of the equilibrium point indicates stable population growth over a long period of time. Numerical simulation is also given to see the trajectories of the population growth movement. The population growth of first prey and second prey is not much different, significant growth occurs at the beginning of the growth period, while after reaching the peak the trajectory growth slopes towards a stable point. Different growth is shown by the predator population, which grows linearly with time. The growth of predators is very significant because predators have the freedom to eat resources. Various types of trajectory patterns in ecological parameters show good results for population growth with the given assumptions.

Complex dynamics induced by multiple gestation delays in a Leslie–Gower‐type system with competitive interference

The dynamics of food consumption by higher trophic level is complicated as its availability, choice, and consequently their development. The top predator interference has a strong influence on the dynamic structure of the tritrophic food chain system. The proposed article deals with the characteristic features of a three‐tire modified Leslie–Gower model with a one‐prey two‐predator system with the assumption of multiple gestation delays. The intermediate predator of the food chain is taken as a specialist type, whereas the growth of top predator is assumed by sexual reproduction. Two different response functions named Monod–Haldane (M‐H) and Beddington–DeAngelis (B‐D) are considered for the modeling of system dynamics. The population densities of intermediate and top predators are assumed to be affected by two different gestation delays. The boundedness and positive equilibria and their stability conditions are examined theoretically for the delay‐free system. The local and global stability conditions of the delayed system are also determined. With the help of normal form theory and central manifold arguments, the properties of bifurcating periodic solutions are carried out. The numerical computation is performed to validate our analytical findings that show the different dynamical outcomes such as periodic and chaotic dynamics. The Hopf‐bifurcation scenario for different parameters of the model system is well studied. Further, the stability behavior of multiple delays for the different cases is investigated. The system shows chaotic behavior when the gestation delay of intermediate predators is large enough. It is also observed that the top predator density is highly fluctuating through the creation of chaos by the inclusion of time delay. Finally, the time delay destabilizing effect is noticed for three‐way interactions among prey, intermediate predator, and top predator, highlighting its significance in chaotic dynamics.

Macronutrient composition of sea otter diet with respect to recolonization, life history, and season in southern Southeast Alaska.

The sea otter (Enhydra lutris) population of Southeast Alaska has been growing at a higher rate than other regions along the Pacific coast. While good for the recovery of this endangered species, rapid population growth of this apex predator can create a human-wildlife conflict, negatively impacting commercial and subsistence fishing. Previous foraging studies throughout the sea otter range have shown they will reduce invertebrate prey biomass when recolonizing an area. The goal of this study was to examine and quantify the energy content of sea otter diets through direct foraging observations and prey collection. Our study area, Prince of Wales Island in southern Southeast Alaska, exhibits a gradient of sea otter recolonization, thus providing a natural experiment to test diet change in regions with different recolonization histories. Sea otter prey items were collected in three seasons (spring, summer, and winter) to measure caloric value and lipid and protein content. We observed 3523 sea otter dives during the spring and summer. A majority of the sea otter diet consisted of clams. Sea otters in newly recolonized areas had lower diet diversity, higher energetic intake rates (EIR, kcal/min), and prey had higher energy content (kcal/g). Females with pups had the highest diet diversity and the lowest EIR. Sea otter EIR were higher in the fall and winter vs. spring and summer. Sea cucumber energy and lipid content appeared to correspond with times when sea otters consumed the highest proportion of sea cucumbers. These caloric variations are an important component of understanding ecosystem-level effects sea otters have in the nearshore environment.