Only the good die old? Ontogenetic determinants of locomotor performance in Eastern cottontail rabbits (Sylvilagus floridanus)

For many animals, the juvenile stage of life can be particularly perilous. Once independent, immature animals must often complete the same basic survival functions as adults despite smaller body size and other growth-related limits on performance. Because, by definition, juveniles have yet to reproduce, we should expect strong selection for mechanisms to offset these ontogenetic limitations, allowing individuals to reach reproductive adulthood and maintain Darwinian fitness. We use an integrated ontogenetic dataset on morphology, locomotor performance, and longevity in wild cottontail rabbits (Sylvilagus floridanus, Allen 1848) to test the hypothesis that prey animals are under selective pressure to maximize juvenile performance. We predicted that 1) juveniles would accelerate more quickly than adults, allowing them to reach adult-like escape speeds, and 2) juveniles with greater levels of performance should survive for longer durations in the wild, thus increasing their reproductive potential. Using high speed video and force platform measurements, we quantified burst acceleration, escape speed, and mechanical power production in 42 wild-caught S. floridanus (29 juveniles, 13 adults; all rabbits >1kg in body mass were designated to be adults, based on published growth curves and evidence of epiphyseal fusion). A subsample of 22 rabbits (16 juveniles, 6 adults) were fitted with radio-telemetry collars for documenting survivorship in the wild. We found that acceleration and escape speed peaked in the late juvenile period in S. floridanus, at an age range that coincides with a period of pronounced demographic attrition in wild populations. Differences in mass-specific mechanical power production explained ∼75% of the variation in acceleration across the dataset, indicating that juvenile rabbits outpace adults by producing more power per unit body mass. We found a positive, though non-significant, association between peak escape speed and survivorship duration in the wild, suggesting a complex relationship between locomotor performance and fitness in growing S. floridanus.

Food Habits of American Kestrels In the Southern High Plains of Texas

ABSTRACT The American Kestrel (Falco sparverius) is in general decline across its North American distribution. In contrast to widespread patterns of decline, kestrel populations appear stable in the southern Great Plains region. Historically, this region had a very low occurrence of kestrels, and their current abundance is highly likely due to vegetation and structures associated with settlement by people of European descent. To determine prey use by breeding kestrels, we placed motion-activated video cameras at preexisting kestrel nest boxes located in the Southern High Plains in 2017. We recorded over 4200 prey deliveries during 1748 hr of observation at five nests over the 4-wk brood-rearing period. On basis of frequency, these deliveries were dominated by reptiles (74.8%), with invertebrates (18.2%), mammals (4.4%), birds (2.9%), and unidentified (1.2%) prey used to lesser extents. Prey delivery rates were high relative to other studies; across the brood-rearing period we recorded an average of 2.3 deliveries/hr, equating to an average of 0.49 deliveries and 3.85 g of prey/nestling/hr. Because invertebrates dominate the diet reported in most kestrel food habit studies, the volume of reptiles captured as prey was unexpected. Even more unanticipated was the number of large prey captured, including juvenile eastern cottontails (Sylvilagus floridanus) and ground squirrels (Ictidomys tridecemlineatus, Xerospermophilus spilosoma). We suspect the proportion of vertebrate prey captured during the nesting season may explain the local high rates of nesting success and number of young fledged.

Dietary choices in a generalist herbivore, the eastern cottontail Sylvilagus floridanus, in urban landscapes

We tested for dietary choices of foods varying in nutrient composition by cottontail rabbits on two college campuses in midwestern USA. We quantified choices among pellets of varying nutritional quality at artificial food patches. Dietary choices differed between seasons and locations. Spring giving-up densities (GUDs: food left behind) did not show differences in food choices and were lower than summer GUDs. In Appleton, the cottontails favoured both high protein and fibre pellets, whereas the medium protein and fibre pellets were favoured in Chicago. The cottontails maintained their choice of high protein, high fibre pellets at three spatial scales. The cottontails varied food intake to balance their protein, salt and fibre needs at different times and locations. Studying dietary choices and the effect of resource quality on foraging responses by urban wildlife provides a useful tool to study ecological interactions and can help minimize damage in urban environments such as parks.

Vigilance Response of a Key Prey Species to Anthropogenic and Natural Threats in Detroit

Rapid urbanization coupled with increased human activity induces pressures that affect predator-prey relations through a suite of behavioral mechanisms, including alteration of avoidance and coexistence dynamics. Synergisms of natural and anthropogenic threats existing within urban environments exacerbate the necessity for species to differentially modify behavior to each risk. Here, we explore the behavioral response of a key prey species, cottontail rabbits (Sylvilagus floridanus), to pressures from humans, domestic dogs, and a natural predator, coyotes (Canis latrans) in a human-dominated landscape. We conducted the first camera survey in urban parks throughout Detroit, Michigan in 2017–2020 to assess vigilance response corresponding to a heterogeneous landscape created from variation in the occupancy of threats. We predicted a scaled response where cottontail rabbits would be most vigilant in areas with high coyote activity, moderately vigilant in areas with high domestic dog activity, and the least vigilant in areas of high human activity. From 8,165 independent cottontail rabbit detections in Detroit across 11,616 trap nights, one-third were classified as vigilant. We found vigilance behavior increased with coyote occupancy and in locations with significantly high domestic dog activity, but found no significant impact of human occupancy or their spatial hotspots. We also found little spatial overlap between rabbits and threats, suggesting rabbits invest more in spatial avoidance; thus, less effort is required for vigilance. Our results elucidate strategies of a prey species coping with various risks to advance our understanding of the adaptability of wildlife in urban environments. In order to promote coexistence between people and wildlife in urban greenspaces, we must understand and anticipate the ecological implications of human-induced behavioral modifications.

ANESTESIA DISSOCIATIVA ASSOCIADA A EPIDURAL EM COELHO (Sylvilagus floridanus) – RELATO DE CASO

<p><span style="font-size: medium;">O presente trabalho tem o objetivo descrever e avaliar um protocolo anestésico implementado para um coelho, macho, sem raça definida, submetido a procedimentos cirúrgicos de orquiectomia e uretrorrafia. O protocolo empregado consistiu no uso de acepromazina como pré-medicação, indução e manutenção com zolazepam e tiletamina e epidural como anestesia local com o uso de lidocaína e tramadol. Foram avaliadas frequência cardíaca, frequência respiratória, saturação periférica de oxihemoglobina, qualidade de recuperação anestésica e a possibilidade de efeitos adversos. Durante o procedimento, houve redução na frequência respiratória, oscilação discreta da frequência cardíaca e estabilidade na saturação periférica de oxihemoglobina, além de bom relaxamento muscular. O animal teve uma recuperação satisfatória e tranquila e não foram observados efeitos adversos. Diante dos resultados, conclui-se que a técnica anestésica implementada foi segura e efetiva para o procedimento em que o animal foi submetido.</span></p>

EN PRENSA Solapamiento en los patrones de actividad de mamíferos y sus presas potenciales en un área de la Sierra Madre Occidental en Durango, México EN PRENSA

Las interacciones ecológicas son parte fundamental para el funcionamiento de los ecosistemas, por lo que indagar en éstas puede brindar información del equilibrio ecológico en un área. El objetivo de este estudio fue determinar las interacciones entre mamíferos y sus presas potenciales por medio del fototrampeo en el predio Sierra del Nayar, Durango. De agosto de 2016 a mayo de 2017 se colocaron cámaras trampa en la temporada de lluvias y secas. De los registros de las fotos se estimó el índice de abundancia relativa, los patrones de actividad por especie, y el índice de solapamiento depredador-presa o de competencia entre depredadores. Se registraron 13 especies de mamíferos y Meleagris gallopavo (guajolote silvestre). No hubo diferencias significativas intraespecíficas de los índices de abundancia relativa entre las temporadas de lluvias y secas para ninguna especie. Existen diferencias significativas interespecíficas de los índices de abundancia relativa durante el periodo de estudio, la temporada de lluvias y la de secas. Las especies más abundantes durante el periodo de estudio fueron: Odocoileus virginianus (venado cola blanca), M. gallopavo, Sciurus aberti (ardilla orejas peludas) y Canis latrans (coyote). Se estimó el índice de solapamiento de seis interacciones, de las cuales Urocyon cinereoargenteus (zorra gris)-Sylvilagus floridanus conejo del este y C. latrans-U. cinereoargenteus tuvieron el más alto índice de solapamiento y no presentaron diferencias significativas en sus patrones de actividad. Los patrones de actividad obtenidos concuerdan con lo reportado para las especies en Norteamérica.

Does the Introduction of Alien Species Represent a Sanitary Threat for Native Species? The Case of the Eastern Cottontail Sylvilagus floridanus in Italy

Introduction of alien species is a well-known threat to biodiversity. Where newly introduced, alien species may pose a risk for the local ecological community by competing for resources or by introducing pathogens. Sylvilagus floridanus is an American lagomorph introduced into Europe in the second half of 20th century, for hunting. This study evaluated the structure and epidemiological characteristics of the gastrointestinal parasite community in an introduced population of S. floridanus in the Province of Alessandria (Piedmont Region—Italy). Three alien parasites were reported out of 271 animals: Obeliscoides cuniculi in the stomach, Trichostrongylus calcaratus in the small intestine, and Passarulus nonnanulatus in the large intestine. All these nematodes are commonly reported in S. floridanus in its natural range, but they represent alien species in Europe. The report of these alien parasites is an example of the unexpected consequences caused by the introduction of non-native vertebrates. The documented introduction of new pathogens may alter the parasite community of the native lagomorphs, with possible long-term effects on local ecological dynamics.

First estimates of survival and densities of invasive alien Eastern cottontail (Sylvilagus floridanus) in Italy: a Bayesian robust design approach

The Eastern cottontail (Sylvilagus floridanus) has become invasive in Central and Northern Italy, where it affects prey-predator dynamics between native species. Although many different studies explored survival rates and the density of cottontails in North America, no information is available for its invasive range. Between December 2003 and October 2005, a capture-recapture scheme for Eastern cottontails was enforced on the Orba River, Italy. We fitted a Bayesian version of the Pollock’s Closed Robust Design to estimate the survival of adult male and female cottontails (n=258) and their density in the study area. Adult cottontails showed minor seasonal differences in survival, with no clear differences between males and females. Densities varied seasonally, with females having higher densities (min = 80 individuals/km2; max = 553 individuals/km2) than males (min = 56 individuals/km2; max = 337 individuals/km2).Eastern cottontails are characterized by high survival and high densities, at least when adults, in their invaded range in Italy. Although densities are comparable to those reported in North America, our analysis focused on adult cottontails only and overall densities are certainly higher. Moreover, our estimates, obtained through a capture-recapture approach, were higher than those reported in previous studies from Italy based on nocturnal spotlight censuses. Spotlight transects are likely to underestimate cottontail densities, due to nocturnal habitat selection of cottontails, which might decrease their detectability.