A thorough understanding of mechanisms of prey consumption by carnivores and the constraints on predation help us in evaluating the role of carnivores in an ecosystem. This is crucial in developing appropriate management strategies for their conservation and mitigating human-carnivore conflict. Current models on optimal foraging suggest that mammalian carnivores would profit most from killing the largest prey that they can subdue with minimal risk of injury to themselves. Wild carnivore diets are primarily estimated through analysis of their scats. Using extensive feeding experiments (n = 68) on a wide size range (4·5-130 kg) of obligate carnivores - lion, leopard, jungle cat and domestic cat, we parameterize biomass models that best relate consumption to scat production. We evaluate additional constraints of gut fill, prey digestibility and carcass utilization on carnivory that were hereto not considered in optimal foraging studies. Our results show that patterns of consumption to scat production against prey size are similar and asymptotic, contrary to established linear models, across these carnivores after accounting for the effect of carnivore size. This asymptotic, allometric relationship allowed us to develop a generalized model: biomass consumed per collectable scat/predator weight = 0·033-0·025exp(-4·284(prey weight/predator weight)) , which is applicable to all obligate carnivores to compute prey biomass consumed from scats. Our results also depict a relationship for prey digestibility which saturates at about 90% for prey larger than predator size. Carcass utilization declines exponentially with prey size. These mechanisms result in digestible biomass saturating at prey weights approximately equal to predator weight. Published literature on consumption by tropical carnivores that has relied on linear biomass models is substantially biased. We demonstrate the nature of these biases by correcting diets of tiger, lion and leopard in recent publications. Our analysis suggests that consumption of medium-sized prey was significantly underestimated, while large prey consumption was grossly overestimated in large carnivore diets to date. We highlight that additional constraints of prey digestibility and utilization combined with escalating handling time and risks of killing large prey make prey larger than the predator size unprofitable for obligate carnivores.

Asiatic lions typify most challenges faced by large carnivores: single population, historical bottlenecks, habitat loss, poaching, and conflict with humans. Their recovery from <50 in a few hundred km 2 to >500 occupying 13,000 km 2 of agro-pastoral Saurashtra landscape, Gujarat, India is an enigma. We review and evaluate the multidisciplinary aspects of lion conservation-strategy that covers ecology, conflict, community perceptions, economics, management, and politics. The history of modern lions in India dates back to ∼4-6,000 BP, but evidence suggests presence as early as 10-15,000 BP. Asiatic lions can be distinguished from African lions by their belly-folds; adult males and females weighing 160 (SE 4.7) and 116 (SE 3.7) kg, respectively. Lion density ranged from 2 to 15/100 km 2 in the Saurashtra landscape. Demographic parameters of Asiatic lions were comparable to African lions. Prides were related females and cubs; males lived separately in hierarchical coalitions having overlapping ranges with multiple prides. Lionesses mated with multiple coalitions to reduce infanticide and enhance genetic diversity of their progeny. Few hectares of scrub sufficed as daytime refuges, while >4 km 2 patches were required for breeding. Sink populations outside Gir Protected Area (PA) were maintained by immigrants. Lions within PA fed primarily on wild-prey, while scavenging and predation on livestock was the mainstay outside. Monetary compensation for livestock-depredation, legal-protection, lion-related profits, combined with religious and cultural sentiments were major drivers of population recovery. The lion has become a socio-political instrument in Gujarat, which despite a Supreme Court directive, has not parted with founders to establish another population. Threats from epidemics loom large and currently a canine distemper virus outbreak is prevalent. Attacks on humans were rare, however, with increasing lion density the intensity of conflict is increasing. This, coupled with lowered tolerance of communities due to erosion of traditional values sets the stage for retaliation. Future of lions outside PA is uncertain as breeding refuges and their connecting corridors are vanishing rapidly. A human-free National Park of ∼1,000 km 2 is essential for ensuring a viable population that retains its ecological role and evolutionary potential. Legalizing lion based ecotourism by forming village consortia holds promise to prevent land conversion and promoting lion-human coexistence.

For a male lion, teamwork pays off but only to an extent. Using behavioral observations, we show that male Asiatic lions team-up to harness resources effectively, but form hierarchies unlike their egalitarian African cousins. Team members prosper better than loners in gaining and retaining access to females. However, teams of 2 males are optimum as low-ranking members of larger teams fare as poorly as loners. A hitherto unknown behavioral variation in lions highlights the flexibility of group living within species.

In species exhibiting infanticide by males, females lose out with high stakes and should adopt preemptive mechanisms, pitching the genders in an evolutionary arms race for maximizing fitness. African lions remain a quintessential model of this gender war, with a coalition of males gaining temporary but exclusive breeding rights over a female group after killing all cubs of former males. However in Asiatic lions, now found as a single population in Gir forests, India, adults live in same-sex groups that interact primarily for mating. Intensive monitoring of 70 adult lions revealed that female groups (n = 9) used exclusive territories, whereas male ranges (n = 11 coalitions) overlapped at areas of intense female use. A social network of mating events (n = 76) indicated that lionesses mated with multiple rival coalitions before conceiving. These neighboring coalitions, although hostile to each other were tolerant toward the same litters, suggestive of confused paternity among them. Given a land-tenure system where lionesses encounter many males capable of killing unfamiliar cubs, multi-male mating buffers cub infanticide and likely diversifies paternal lineages in litters. Consequently, infanticide was observed only when “new” males invaded a female group’s territory. An age-based mate choice was observed in lionesses: maiden breeders chose males having highest range overlaps, whereas experienced females selected peripheral males. The intergender spacing patterns and resultant sexual strategies of lions differ in Asia and Africa probably because of contrasting resource availability, highlighting behavioral plasticity within species inhabiting diverse eco-regions. By mating with multiple males, lionesses safeguard their investments and outdo the males in the war of fitness.

Survival is a key determinant of population growth and persistence; computation and understanding of this metric is key to successful population management, especially for recovering populations of large carnivores such as wolves. Using a Bayesian frailty analytical approach, we evaluated information from 150 radio-tagged wolves over a 16-year time period to determine temporal trends and age- and sex-specific survival rates of wolves in Minnesota, United States. Based on our analyses, overall annual survival of wolves during the study was 0.67, with no clear evidence for age- or sex-specific differences in the population. Our model demonstrated statistical support for a temporal trend in annual survival; the highest survival was predicted at the beginning of the time series (0.87), with lowest survival (0.55) during 2018. We did not observe evidence that survival was markedly reduced during years when a regulated hunting and trapping season was implemented for wolves (years 2012–2014). However, cause-specific mortality analysis indicated that most mortality was human-caused. While the estimate for increasing human-caused mortality over time was positive, the evidence was not statistically significant. Anthropogenic causes resulted in ∼66% of known mortalities, including legal and illegal killing, and vehicular collisions. Trends in wolf survival in Minnesota may reflect an expanding distribution; wolf range has spread to areas with more human development during the study, presumably leading to increased hazard and reduced survival. Our results provide foundational information for evaluating and guiding future policy decisions pertaining to the Great Lakes wolf population.