Fighting by Kittens and Piglets during Suckling: What Does it Mean?

Testing aggressive behaviour in a feeding context: Importance of ethologically relevant stimuli

The choice of stimuli used in tests of animal behaviour can have a critical effect on the outcome. Here we report two experiments showing how different foods influenced aggressive behaviour in competition tests at weaning among littermates of the domestic cat. Whereas in Experiment 1 canned food elicited almost no overt competition, a piece of raw beef rib elicited clearly aggressive behaviour among littermates. In Experiment 2 the food stimuli were chosen to differ from raw beef rib in various combinations of taste/smell, texture and monopolizability. Kittens showed different levels of aggression in response to the five stimuli tested, which suggests that the strong effect of beef rib in eliciting aggressive behaviour was due to a complex combination of features. We suggest that using stimuli approximating the evolved, functional significance to the species concerned is more likely to result in robust, biologically relevant behaviours than more artificial stimuli.

Stable individual differences in separation calls during early development in cats and mice

Background

The development of ethologically meaningful test paradigms in young animals is an essential step in the study of the ontogeny of animal personality. Here we explore the possibility to integrate offspring separation (distress) calls into the study of consistent individual differences in behaviour in two species of mammals, the domestic cat (Felis silvestris catus) and the mound-building mouse (Mus spicilegus). Such vocal responses in young mammals are a potentially useful test option as they represent an important element of mother-offspring communication with strong implications for offspring survival. In addition, the neural control of vocalisation is closely associated with emotional state.

Results

We found marked similarities in the pattern of individual responses of the young of both species to separation from their mother and littermates. In the domestic cat as well as in the mound-building mouse, individual differences in the frequency of calls and to a lesser extent in locomotor activity were repeatable across age, indicating the existence of personality types. Such consistencies across age were also apparent when only considering relative individual differences among litter siblings. In both species, however, individual patterns of vocalisation and locomotor activity were unrelated. This suggests that these two forms of behavioural responses to isolation represent different domains of personality, presumably based on different underlying neurophysiological mechanisms.

Conclusions

Brief separation experiments in young mammals, and particularly the measurement of separation calls, provide a promising approach to study the ontogeny of personality traits. Future long-term studies are needed to investigate the association of these traits with biologically meaningful and potentially repeatable elements of behaviour during later life.

Suckling behavior in Eurasian lynx (Lynx lynx L.) cubs: characteristics and correlation with competitive interactions

There is substantial evidence in the literature that the offspring of many mammal species prefer a particular pair of nipples. There is also a definite "nipple order" in individual litters in which each young predominantly uses one or two particular nipples. In combination with early competitive interactions, such "constancy" can play an important role in the social development of the young. In this study, we reveal an unequal use of different pairs of mothers' nipples by 42 Eurasian lynx cubs in 16 litters and investigate the relationship of this phenomenon with the early competitive interactions of the cubs and their physical development. For the lynx cubs, the most often used pair of nipples is the middle pair. There is also definite "nipple order" in each litter. We found a negative correlation between nipples use by the offspring and their competitive activity. No influence of "nipple order" on the cubs' growth rate was detected.