Parental Care and Adult Aggression toward Juvenile Snowshoe Hares

The early life of the snowshoe hare was studied through observations and experiments involving penned and wild hares. Parental care was limited to the adult female. Her care extended only to lactation and possibly to some guarding of her offspring. The leverets gathered at the birth/nursing site 1-2 hours after sunset and suckled immediately upon the arrival of the female for 2-5 minutes. The leverets born in the pens gained 17.1 g per day for the first 60 days of life. Weaned juveniles caught in the wild were introduced into a pen containing resident adults and juveniles. All 30 introduced juveniles were involved in interactions with residents, both adults and juveniles. The introduced juveniles were involved in and were the losers in more antagonistic interactions than were resident juveniles. Similar adult/juvenile and juvenile/juvenile interactions were observed in an unmanipulated wild population of hares, although the residential status of many of the participants was unknown. We concluded that aggression from resident adults and juveniles could lead to spacing behaviour and might therefore affect juvenile recruitment.Key words: Lepus americanus, snowshoe hare, spacing behaviour, dispersal, aggression, lactation On a étudié les premiers mois de la vie du lièvre d'Amérique en faisant des observations et des expériences sur les lièvres parqués dans des enclos et sur d'autres vivant à l'état sauvage. La femelle adulte était seule à s'occuper des petits, et les soins qu'elle leur donnait se limitaient à la tétée et peut-être à une certaine surveillance. Les levrauts commençaient à se rassembler au lieu de leur naissance et des tétées de une à deux heures après le coucher du soleil, et ils tétaient de 2 à 5 mm, dès l'arrivée de la femelle. Les levrauts nés dans les enclos gagnaient 17,1 g quotidiennement pendant leurs 60 premiers jours.Des jeunes sevrés et capturés dans la nature ont été introduits dans un enclos où se trouvaient déjà des adultes et des petits. Les 30 jeunes introduits ont tous été impliqués dans des interactions avec les résidents aussi bien les adultes que les petits. Les jeunes introduits ont été impliqués dans plus d'interactions agressives que les petits déjà dans l'enclos, et ils en sont sortis plus souvent perdants. Sans toutefois connaître le statut d'appartenance de beaucoup des membres, on a observé des interactions similaires entre les adultes et les jeunes et entre les jeunes eux-mêmes dans une population de lièvres vivant à l'état sauvage et n'ayant pas été en contact avec l'homme. On conclut que l'agression des adultes et des petits du groupe peut conduire à un comportement de distanciation et pourrait donc affecter le taux de reproduction. Mots clés : Lepus Americanus, lièvre d'Amérique, comportement de distanciation, éparpillement, agression, lactatio

Informing aerial total counts with demographic models: population growth of Serengeti elephants not explained purely by demography

Conservation management is strongly shaped by the interpretation of population trends. In the Serengeti ecosystem, Tanzania, aerial total counts indicate a striking increase in elephant abundance compared to all previous censuses. We developed a simple age-structured population model to guide interpretation of this reported increase, focusing on three possible causes: (1) in situ population growth, (2) immigration from Kenya, and (3) differences in counting methodologies over time. No single cause, nor the combination of two causes, adequately explained the observed population growth. Under the assumptions of maximum in situ growth and detection bias of 12.7% in previous censuses, conservative estimates of immigration from Kenya were between 250 and 1,450 individuals. Our results highlight the value of considering demography when drawing conclusions about the causes of population trends. The issues we illustrate apply to other species that have undergone dramatic changes in abundance, as well as many elephant populations

Asynchronous food-web pathways could buffer the response of Serengeti predators to El Niño southern oscillation

Understanding how entire ecosystems maintain stability in the face of climatic and human disturbance is one of the most fundamental challenges in ecology. Theory suggests that a crucial factor determining the degree of ecosystem stability is simply the degree of synchrony with which different species in ecological food webs respond to environmental stochasticity. Ecosystems in which all food-web pathways are affected similarly by external disturbance should amplify variability in top carnivore abundance over time due to population interactions, whereas ecosystems in which a large fraction of pathways are nonresponsive or even inversely responsive to external disturbance will have more constant levels of abundance at upper trophic levels. To test the mechanism underlying this hypothesis, we used over half a century of demographic data for multiple species in the Serengeti (Tanzania) ecosystem to measure the degree of synchrony to variation imposed by an external environmental driver, the El Niño Southern Oscillation (ENSO). ENSO effects were mediated largely via changes in dry-season vs. wet-season rainfall and consequent changes in vegetation availability, propagating via bottom-up effects to higher levels of the Serengeti food web to influence herbivores, predators and parasites. Some species in the Serengeti food web responded to the influence of ENSO in opposite ways, whereas other species were insensitive to variation in ENSO. Although far from conclusive, our results suggest that a diffuse mixture of herbivore responses could help buffer top carnivores, such as Serengeti lions, from variability in climate. Future global climate changes that favor some pathways over others, however, could alter the effectiveness of such processes in the future

Conservation and economic benefits of a road around the Serengeti

No abstract available

Parallel ecological networks in ecosystems

In ecosystems, species interact with other species directly and through abiotic factors in multiple ways, often forming complex networks of various types of ecological interaction. Out of this suite of interactions, predator–prey interactions have received most attention. The resulting food webs, however, will always operate simultaneously with networks based on other types of ecological interaction, such as through the activities of ecosystem engineers or mutualistic interactions. Little is known about how to classify, organize and quantify these other ecological networks and their mutual interplay. The aim of this paper is to provide new and testable ideas on how to understand and model ecosystems in which many different types of ecological interaction operate simultaneously. We approach this problem by first identifying six main types of interaction that operate within ecosystems, of which food web interactions are one. Then, we propose that food webs are structured among two main axes of organization: a vertical (classic) axis representing trophic position and a new horizontal ‘ecological stoichiometry’ axis representing decreasing palatability of plant parts and detritus for herbivores and detrivores and slower turnover times. The usefulness of these new ideas is then explored with three very different ecosystems as test cases: temperate intertidal mudflats; temperate short grass prairie; and tropical savannah

Keeping the herds healthy and alert: implications of predator control for infectious disease

Predator control programmes are generally implemented in an attempt to increase prey population sizes. However, predator removal could prove harmful to prey populations that are regulated primarily by parasitic infections rather than by predation. We develop models for microparasitic and macroparasitic infection that specify the conditions where predator removal will (a) increase the incidence of parasitic infection, (b) reduce the number of healthy individuals in the prey population and (c) decrease the overall size of the prey population. In general, predator removal is more likely to be harmful when the parasite is highly virulent, macroparasites are highly aggregated in their prey, hosts are long-lived and the predators select infected prey

The ‘mosaic habitat’ concept in human evolution: past and present

The habitats preferred by hominins and other species are an important theme in palaeoanthropology, and the ‘mosaic habitat’ (also referred to as habitat heterogeneity) has been a central concept in this regard for the last four decades. Here we explore the development of this concept – loosely defined as a range of different habitat types, such as woodlands, riverine forest and savannah within a limited spatial area– in studies of human evolution in the last sixty years or so. We outline the key developments that took place before and around the time when the term ‘mosaic’ came to wider palaeoanthropological attention. To achieve this we used an analysis of the published literature, a study of illustrations of hominin evolution from 1925 onwards and an email survey of senior researchers in palaeoanthropology and related fields. We found that the term mosaic starts to be applied in palaeoanthropological thinking during the 1970’s due to the work of a number of researchers, including Karl Butzer and Glynn Isaac , with the earliest usage we have found of ‘mosaic’ in specific reference to hominin habitats being by Adriaan Kortlandt (1972). While we observe a steady increase in the numbers of publications reporting mosaic palaeohabitats, in keeping with the growing interest and specialisation in various methods of palaeoenvironmental reconstruction, we also note that there is a lack of critical studies that define this habitat, or examine the temporal and spatial scales associated with it. The general consensus within the field is that the concept now requires more detailed definition and study to evaluate its role in human evolution