Linking tooth shape to strike mechanics in the Boa constrictor

Snakes, with the obvious exception of the fangs, are considered to lack the regional specialization of tooth shape and function that are exemplified by mammals. Recent work in fishes has suggested the definition of homodont and heterodont are incomplete without a full understanding of the morphology, mechanics, and behavior of feeding. We investigated this idea further by examining changes in tooth shape along the jaw of Boa constrictor and integrating these data with the strike kinematics of boas feeding on rodent prey. We analyzed the shape of every tooth in the skull, from a combination of anesthetized individuals and CT scanned museum specimens. For strike kinematics, we filmed eight adult boas striking at previously killed rats. We determined the regions of the jaws that made first contact with the prey, and extrapolated the relative positions of those teeth at that moment. We further determined the roles of all the teeth throughout the prey capture process, from the initiation of the strike until constriction began. We found that teeth in the anterior third of the mandible are the most upright, and that teeth become progressively more curved posteriorly. Teeth on the maxilla are more curved than on the mandible, and the anterior teeth are more linear or recurved than the posterior teeth. In a majority of strikes, boas primarily made contact with the anterior third of the mandible first. The momentum from the strike caused the upper jaws and skull to rotate over the rat. The more curved teeth of the upper jaw slid over the rat unimpeded until the snake began to close its jaws. In the remaining strikes, boas made contact with the posterior third of both jaws simultaneously, driving through the prey and quickly retracting, ensnaring the prey on the curved posterior teeth of both jaws. The curved teeth of the palatine and pterygoid bones assist in the process of the swallowing.

Nest association between two predators as a behavioral response to the low density of rodents

Many birds nest in association with aggressive birds of other species to benefit from their protection against predators. We hypothesized that the protective effect also could extend to foraging resources, whereby the resultant resource-enriched habitats near a nest of aggressive raptors could be an alternative cause of associations between nesting bird species with non-overlapping foraging niches. In the Arctic, the Rough-legged Hawk (Buteo lagopus) and the Peregrine Falcon (Falco peregrinus) are 2 raptor species with non-overlapping food resources that have been reported to nest sometimes in close proximity. Since nesting Peregrine Falcons are very aggressive, they may protect the small rodent prey near their nests from predation, and Rough-legged Hawks could use these hot spots as a nesting territory. In 2 regions in low Arctic Russia we found that (1) the nesting territories of Peregrine Falcons were indeed enriched with small rodents as compared to control areas, (2) the probability of nest association between the 2 raptors increased when rodent abundance was generally low in the region where hawks did not use alternative prey, and (3) hawk reproductive success increased when nesting close to Peregrine Falcons. These results suggest that implications of aggressive nest site defense in birds in certain cases may involve more mechanisms than previously explored. A key ecological process in tundra, rodent population cycles, may explain the occurrence and adaptive significance of a specific behavior pattern, the nesting association between 2 raptor species.

Food composition of Indian Eagle Owl Bubo bengalensis Franklin (Aves: Strigiformes: Strigidae) from Tiruchirappalli District, Tamil Nadu, India

The diet of the Indian Eagle Owl was studied from April to September 2017 in Tiruchirapalli District, Tamil Nadu, India. Analysis of 1082 regurgitated pellets yielded 2077 prey items; the mean prey items/ pellet was 1.91. The diet constituted 65.1% of rodent prey and the remaining 34.83% of other groups of both vertebrate and invertebrate animals. The mean percentage of prey composition was 31.15% Millardia meltada Soft-furred Field Rat, 12.95% Bandicota bengalensis Lesser Bandicoot Rat, 10.25% Mus booduga Indian Field Mouse, and 10.24% of other rodent species. Of the 34.83% of non-rodent prey, the owls ingested insects (Rhinoceros beetles, 9.58%), Arachnida (Solifugae or Sun spider, Galeodes sp., 9.58%), reptiles (Calotes sp., 3.7%), amphibians (3.56%), shrews (Suncus murinus, 2.84%), and others (5.57%). The Indian Eagle Owls consumed more than one prey per day and chiefly foraged in agricultural crop fields and consumed both small mammals and insects of agricultural importance under crop ecosystems.

An Over View of Feline Dermatophytosis

Dermatophytosis is a superficial fungal infection of hair and keratinized layers of the epidermis and is caused by keratinophilic and keratinolytic genera such as Microsporum, Trichophyton and Epidermophyton. It is an endemic infection in many countries throughout the world affecting companion animals (dogs, cats), domestic animals (calves), and laboratory animals (rabbits) as well as humans. In cats M. canis is responsible for approximately 98% of the observed dermatophyte infections in indoor cats, whereas cats carrying T. mentagrophytes are usually hunters, indicating that the natural source of this species is either the soil or rodent prey.

The population dynamics of bite-sized predators: prey dependence, territoriality, and mobility

The dependency of mustelid demographic rates on prey abundance has the potential to cause a strong coupling between predator-prey populations. Data on mustelid dynamics show that such strong reciprocal interactions only materialise in some restricted conditions. Bite-size mustelid predators searching for scarce, depleted prey expose themselves to increased risk of predation by larger predators of small mammal that are themselves searching for similar prey species. As voles or muskrats become scarcer, weasels and mink searching for prey over larger areas become increasingly exposed to intra-guild predation, unless they operate in a habitat refuge such as the sub-nivean space. Where larger predators are sufficiently abundant or exert year-round predation pressure on small mustelids, their impact on mustelids may impose biological barrier to dispersal that are sufficient to weaken the coupling between small mustelids and their rodent prey, and thus impose a degree of top down limitation on mustelids.

Desert mammal populations are limited by introduced predators rather than future climate change

Climate change is predicted to place up to one in six species at risk of extinction in coming decades, but extinction probability is likely to be influenced further by biotic interactions such as predation. We use structural equation modelling to integrate results from remote camera trapping and long-term (17–22 years) regional-scale (8000 km 2 ) datasets on vegetation and small vertebrates (greater than 38 880 captures) to explore how biotic processes and two key abiotic drivers influence the structure of a diverse assemblage of desert biota in central Australia. We use our models to predict how changes in rainfall and wildfire are likely to influence the cover and productivity of the dominant vegetation and the impacts of predators on their primary rodent prey over a 100-year timeframe. Our results show that, while vegetation cover may decline due to climate change, the strongest negative effect on prey populations in this desert system is top-down suppression from introduced predators.

Training barn owls: a powerful tool in ecological experiments

Predators affect prey directly by predation and indirectly by triggering behavioral responses that aim at reducing predation risk. In this paper, I present a method for training an avian predator which can allow separating between its direct and indirect effects on prey in various experimental setups. Barn owls are found to be a valuable tool for empirically testing different hypotheses related to predator-prey interactions, population dynamics, and inter-specific competition, all performed in the field using authentic rodent prey and their natural predators. Barn owls are raised and trained to participate in field experiments using classical conditioning, and are trained either to catch rodents or only to fly above a certain area without making any attempt to attack the prey, simulating solely predation risk. Body mass is a crucial factor in the training procedure, and I thus define five body mass ranges that characterize different behavioral stages in the training of owls. A logistic model is used to calculate and to predict changes in the body mass during the growth and training periods of owls. Finally, I discuss several possible implications of the usage of trained barn owls in empirical studies.