Facilitation between bovids and equids on an African savanna

Background: Equids, especially zebras and donkeys, and cattle (bovids) share habitats in many savanna ecosystems in Africa. The issue of competition for food between these ungulate guilds remains largely unresolved. Resolving it will provide insights into how wild zebra are likely to interact with cattle on shared landscapes and suggest best practices for cattle owners who must decide whether to tolerate wild ungulates, some of which are severely threatened (e.g. Grevy’s zebra, Equus grevyi). Aim: Determine whether an equid and a bovid compete in a semi-arid savanna in Kenya. Organisms: Boran cattle (Bos indicus) and donkeys (Equus africanus asinus) – the latter as surrogates for zebras. Methodology: Experiments to measure performance (weight gains), bite rates, diet quality (digestible organic matter and crude protein), and gastrointestinal worm burdens (parasite egg count per unit weight of faeces) of the two ungulate species when herded separately (single species) or together (mixed species). We used two stocking levels: low-density (one animal per 7 ha), a level typical of commercial ranchers; and high-density (one animal per 2 ha), a level typical of pastoral herders. Principal findings: When herded together, both species gained more weight, had higher bite rates (especially at low stocking density), and selected diets with a more favourable balance between digestible organic matter and crude protein, than when herded separately. In addition, parasite egg output in faeces of donkeys was reduced by 14–35% following shared foraging with cattle. Conclusion: Cattle (a ruminant) and donkeys (hindgut fermenters, closely related to zebras) showed no evidence of competion with each other. Rather, our results show a facilitative, rather than a competitive, interaction between them

Nutritional ecology beyond the individual: a conceptual framework for integrating nutrition and social interactions

International audienceOver recent years, modelling approaches from nutritional ecology (known as Nutritional Geometry) have been increasingly used to describe how animals and some other organisms select foods and eat them in appropriate amounts in order to maintain a balanced nutritional state max-imising fitness. These nutritional strategies profoundly affect the physiology, behaviour and performance of individuals, which in turn impact their social interactions within groups and societies. Here, we present a conceptual framework to study the role of nutrition as a major ecological factor influencing the development and maintenance of social life. We first illustrate some of the mechanisms by which nutritional differences among individuals mediate social interactions in a broad range of species and ecological contexts. We then explain how studying individual-and collective-level nutrition in a common conceptual framework derived from Nutritional Geometry can bring new fundamental insights into the mechanisms and evolution of social interactions, using a combination of simulation models and manipulative experiments

Chemical detection of sex and condition in the crayfish Orconectes virilis

Individual crayfish ( Orconectes virilis ) were tested for responses to water containing conspecific individuals of several sex-status categories. Isolated males did not react to “self” water but did show aggressive postures while isolated, nonself male water was introduced. Males' responses to female water was different from responses to male water. Water from aggressing males elicited fewer agonistic postures and more “neutral” postures. Females showed little difference in response to waters from different categories of conspecifics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44870/1/10886_2004_Article_BF00988201.pd