Effect of the habitat and tusks on trunk grasping techniques in African savannah elephants.

Among tetrapods, grasping is an essential function involved in many vital behaviours. The selective pressures that led to this function were widely investigated in species with prehensile hands and feet. Previous studies namely highlighted a strong effect of item properties but also of the species habitat on manual grasping behaviour. African savannah elephants (Loxodonta africana) are known to display various prehensile abilities and use their trunk in a large diversity of habitats. Composed of muscles and without a rigid structure, the trunk is a muscular hydrostat with great freedom of movement. This multitasking organ is particularly recruited for grasping food items while foraging. Yet, the diet of African savannah elephants varies widely between groups living in different habitats. Moreover, they have tusks alongside the trunk which can assist in grasping behaviours, and their tusk morphologies are known to vary considerably between groups. Therefore, in this study, we investigate the food grasping techniques used by the trunk of two elephant groups that live in different habitats: an arid study site in Etosha National Park in Namibia, and an area with consistent water presence in Kruger National Park in South Africa. We characterised the tusks profiles and compared the grasping techniques and their frequencies of use for different foods. Our results show differences in food-grasping techniques between the two groups. These differences are related to the food item property and tusk profile discrepancies highlighted between the two groups. We suggest that habitat heterogeneity, particularly aridity gaps, may induce these differences. This may reveal an optimisation of grasping types depending on habitat, food size and accessibility, as well as tusk profiles.

Analogous laterality in trunk movements in captive African elephants: A pilot study.

Lateralization of hand use in primates has been extensively studied in a variety of contexts, and starts to be investigated in other species and organs in order to understand the evolution of the laterality according to different tasks. In elephants, the orientation of the movements of the trunk has been observed mainly in feeding and social contexts, in free conditions. However, little is known about the influence of task complexity on trunk laterality. In this study, we compared the lateralization of the trunk in two conditions: standardized and free. We offered granules to six African elephants on each side of an opened trapdoor to create a constraining environment and reported the different behaviours employed and their orientation. In addition, we observed the same individuals in free conditions and noted the lateralization of the use of their trunk. We revealed a common right side preference in all our elephants, both in standardized and free conditions. This side bias was stronger in our constraining task, adding evidence for the task complexity theory. We finally described laterality in new behaviours in the literature on elephants, such as pinching, gathering or exploration with the trunk.

Behavioural variability among captive African elephants in the use of the trunk while feeding.

The Proboscideans, an order of mammals including elephants, are the largest of the Earth lands animals. One probable consequence of the rapid increase of their body size is the development of the trunk, a multitask highly sensitive organ used in a large repertoire of behaviours. The absence of bones in the trunk allows a substantial degree of freedom for movement in all directions, and this ability could underlie individual-level strategies. We hypothesised a stronger behavioural variability in simple tasks, and a correlation between the employed behaviours and the shape and size of the food. The observations of a captive group of African elephants allowed us to create a complete catalogue of trunk movements in feeding activities. We noted manipulative strategies and impact of food item properties on the performed behaviours. The results show that a given item is manipulated with a small panel of behaviours, and some behaviours are specific to a single shape of items. The study of the five main feeding behaviours emphasises a significant variability between the elephants. Each individual differed from every other individual in the proportion of at least one behaviour, and every behaviour was performed in different proportions by the elephants. Our findings suggest that during their lives elephants develop individual strategies adapted to the manipulated items, which increases their feeding efficiency.

Transmission of food preference via faeces in male and female house mice: Who is a good provider of food cues?

The social transmission of food preference (STFP) is a phenomenon that allows rodents to use food information perceived from their conspecifics to guide their own food choices. This social information can be collected via olfactory cues, during direct social interactions, or indirectly, via faeces left in the environment by individuals. Although reducing the risks associated with a social confrontation, faeces also convey different types of information about traits and states of individuals which could affect the indirect STFP. Here, we evaluated in the house mouse, Mus musculus domesticus, which conspecifics could be good providers of food cues for indirect STFP. Our results indicated that female mice acquire an indirect STFP from faeces of adult females, familiar or not and from faeces of adult unfamiliar males. On the contrary, males do not establish an indirect STFP from faeces of males, whether they are familiar or not, nor from those of unfamiliar females. Indirect STFP was however effective in males when the faeces were those of an unfamiliar juvenile male. A prior habituation to the odour of an unfamiliar female allowed the establishment of indirect STFP in males. Conversely, the presence of faeces of another adult male during the presentation of faeces of an accustomed female precluded the acquisition of indirect STFP in males. This study suggested that in the context of the indirect STFP, females prioritize socio-olfactory information relative to food, whereas food cues were not priority information for males. Under these conditions, females appear to be the best vectors for disseminating food information within the population. These results are discussed according to the socio-spatial organization of the species.

Necessary Conditions for Social Transmission of Food Preference Through Feces in the House Mouse, Mus musculus domesticus.

Mice can obtain information about a new food source through olfactory cues of conspecifics and consequently develop an attraction for this diet. The social transmission of food preference (STFP) takes place directly, during an encounter with a conspecific or indirectly, via feces. In indirect STFP, the digestive process can degrade odorant compounds characterizing the food, impairing the matching between feces and food. In a previous study, indirect STFP was efficient when the information support was a composite odorant. We, thus, hypothesized that the acquisition of indirect STFP depends on the multiplicity of the odorant compounds present in diets. Tested in female house mice (Mus musculus domesticus) our results showed that a single odorant compound as information support was not sufficient to induce an indirect STFP. Chemical analysis did not reveal the presence of the compounds in feces suggesting that the degradation of diet cues during the digestive process prevented the pairing between feces and food. By using a process that limits the degradation of molecules, we performed indirect STFP when the pertinent information was represented by a single odorant compound and multiple odorant compounds. Unlike with multiple odorant compounds, our results did not show a clear indirect STFP with single odorant compound, despite their presence in feces confirmed by chemical analysis. We conclude that constraints associated to indirect STFP can be removed by the multiplicity of information characterizing the diet both by reducing the degradation risk during the digestive process and by allowing an accurate assessment of diet consumed by the conspecific.

Individual differences in early body mass affect thermogenic performance and sibling interactions in litter huddles of the house mouse.

We asked whether within-litter differences in early body mass are associated with differences in house mouse pups' thermogenic performance and whether such variation predicts individual differences in competitive interactions for thermally more advantageous positions in the huddle. We explored pups' thermogenic performance in isolation by measuring changes in (maximal) peripheral body temperatures during a 5-min thermal challenge using infrared thermography. Changes in peripheral body temperature were significantly explained by individual differences in body mass within a litter; relatively lighter individuals showed an overall quicker temperature decrease leading to lower body temperatures toward the end of the thermal challenge compared to heavier littermates. Within the litter huddle, relatively lighter pups with a lower thermogenic performance showed consistently more rooting and climbing behavior, apparently to reach the thermally advantageous center of the huddle. This suggests that within-litter variation in starting body mass affects the pups' thermal and behavioral responses to environmental challenges.

Transmission of food preference between unfamiliar house mice (Mus musculus domesticus) is dependent on social context.

Rodents obtain information about a new food source through olfactory cues of conspecifics and consequently develop an attraction for this diet. Generally, physical contact between an observer and a demonstrator that has recently consumed a novel food item is required to allow the social transmission of food preference (STFP). However, in natural populations of house mice, social encounters between unfamiliar individuals usually turn into a fight. Thus, social intolerance between the individuals involved could prevent STFP. It has been shown that the feces of rodents can act as a social stimulus and promote STFP in mice, which could reduce the social constraints associated with an encounter. Here, we examined the acquisition of the STFP in female house mice of wild origin (Mus musculus domesticus) after a direct encounter with a familiar and unfamiliar female, and after the presentation of olfactory marks of an unfamiliar female. Unlike in encounters between familiar females, our results did not provide significant support for the existence of STFP after encounters between two unfamiliar females, independently of the occurrence or absence of offensive agonistic behavior. However, STFP through olfactory marks of an unfamiliar female was effective. We suggest that the social context might strongly impair direct STFP, not necessarily via the unfamiliarity of the information provider but rather via its physical presence. (PsycINFO Database Record

Efficiency of delayed reproduction in Mus spicilegus.

To cope with seasonally varying ecological constraints, some mammals temporally suppress breeding or delay their first reproduction. In field conditions, mound-building mice (Mus spicilegus) born in spring begin to reproduce when 2-3 months old, whereas individuals born at the end of summer delay their first reproduction for 6-8 months until the following spring. In order to test age effects on reproductive performance in M. spicilegus, sexually naïve mice were paired when 2-3 months old or at 6-8 months of age, and surveyed for reproduction. We show here that under laboratory conditions the aging of these mice does not impair their reproductive efficiency. Thus, the hypothesis of a lower reproductive potential in these relatively aged females seems to be contradicted. More surprisingly, the latency from pairing to the first reproduction was greater in the 2-3-month-old adults than in the delayed reproducers (6-8-month-old mice). Mound-building mice that are old enough to have overwintered do not suffer significant reproductive declines, but appear to reproduce as well and more quickly than younger first-time breeders.

Concordance in mate choice in female mound-building mice.

Females must evaluate male quality to perform mate choice. Since females generally base their selection on different male features, individual females may differ in their choice. In this study, we show that concordance between females in mate choice decisions may arise without any experimental maximization of a particular attractive trait. Choice tests were performed in mound-building mice, Mus spicilegus, a monogamous species. Body odours of two male donors were presented to 12 female subjects individually. To determine female choice, the same pair of males was presented three times to a female. Four different pairs of male body odours were used. Male donors, not related to females, were selected at random in our polymorphic breeding stock. Using this two-way choice design, female mice displayed a clear choice and had a similar preference for particular males.

Effects of pre- and postnatal olfactogustatory experience on early preferences at birth and dietary selection at weaning in kittens.

The ontogenesis of olfactogustatory preferences has been investigated in various mammals but surprisingly not in domestic cats Felis catus. In a first experiment, we examined how prenatal exposure (25 days prepartum) to a cheese flavor via the mother's diet can influence olfactory preferences of neonatal kittens. During 2-choice tests, 2-day-old kittens oriented first toward the cheese odor experienced in utero more frequently than toward a usual pet food odor. The choice of kittens born to mothers fed with a control diet did not differ from random. In the second experiment, we assessed the role of pre- and postnatal exposure (from 25th day before to 23rd day after birth) to cheese flavor on food preferences in weaned kittens. Forty-five-day-old cats exposed to cheese flavor during uterine and postnatal life via their mothers' diet ate higher amounts of chicken supplemented with cheese flavor than food supplemented with usual pet food flavor. On the other hand, the control group did not exhibit a preference for a specific food. Our results clearly demonstrated that pre- and postnatal olfactogustatory exposure via maternal ingestion influences later olfactory and food preferences of cats.

Evaluation of the social bond: a new method tested in Mus spicilegus.

Innovative and fruitful studies of social bonds have been developed in recent years, although the methods used to establish the existence of a social bond between two individuals have not evolved significantly. Two types of paradigms have been currently used: the separation-reunion paradigm, which evaluates the distress caused by the disruption of the social bond, and choice paradigms, which test the specificity of the bond to a given individual. We have developed a new paradigm based on the idea that the cost an individual was ready to pay in order to gain access to a conspecific depended on the strength of the social bond between the two individuals. To test our paradigm we used mound-building mice, Mus spicilegus that present, in both males and females, a level of tolerance that differs greatly according to the degree of familiarity between the individuals. Our new method for testing social bond revealed unsuspected differences between males and females. Our results suggested that, at least in Mus spicilegus, strong social bonds were not necessary to the development of a high level of tolerance between individuals.

Paternal care in the mound-building mouse reduces inter-litter intervals.

In many rodent species males display paternal behaviour. The primary reported effect of this paternal care is to increase pup survival. In mammal females, pregnancy and lactation are energetically demanding, especially when they are concurrent in post-partum reproduction. To face this energy requirement, females generally lengthen the duration of their post-partum pregnancy. In the present study we tested whether paternal care could affect this duration in the monogamous mound building mouse Mus spicilegus. In this species, females have a short reproductive life that does not exceed 4 months. Reduction of inter-delivery latencies would then be an efficient way to increase reproductive success. In a male removal experiment, we showed that inter-delivery latency was shortened by male presence. Moreover, behavioural estimations of paternal involvement were correlated with inter-delivery latency. The longer the male spent inside the nest the shorter the inter-delivery latency. In the mound-building mouse, the female might be able to monopolise the parental care of a single male, which could be important for the evolution of monogamy. The characteristics of first reproduction as compared to post-partum reproduction suggest that it may contribute to the formation of a strong and exclusive social bond between the reproductive partners.

Deficit in reproduction in polygynously mated females of the monogamous mound-building mouse Mus spicilegus.

In monogamous mound-building mice Mus spicilegus, facultative polygyny was observed in April, at the beginning of the reproductive season. In order to evaluate the cost of polygyny, we compared, under laboratory conditions, the reproductive success of trios and pairs composed of sister females mated with unrelated brother males. Females in trios were able to tolerate each other during the reproductive period and to reproduce with the same male under spatial constraints. Nevertheless, polygyny had a strong negative effect on the reproductive success of the females. The average number of young per litter was smaller in trio females than in paired females, whereas the interval between two successive litters was higher. As a result, the number of litters and the number of young per time unit were smaller in each of the trio females compared with paired females. Agonistic behaviour being absent in trios, our results strongly suggest that living in trios led to pheromonal production that affected the female physiological state and reproduction. Males of trios did not obtain a better reproductive success than males in pairs.

Seasonal reproduction and delayed sexual maturity in mound-building mice Mus spicilegus.

In the mound-building mouse, Mus spicilegus, which is found from Central to Eastern Europe, reproduction is seasonal and limited to spring and summer. In autumn, the mice build voluminous mounds composed of vegetable matter covered with earth, where juvenile animals (autumnal individuals) over-winter in groups without reproducing. Autumnal animals delay reproduction until the next spring when they are 6 months old. The influence and interactions of environmental (short light period and cold temperature (C conditions) compared with long light period and temperate temperature (T conditions)) and social factors (lack of odours from breeding adults (NB conditions) compared with presence of odours from breeding adults (B conditions)) on reproduction and sexual maturation were studied. Forty groups of three autumnal individuals (two males and a female or two females and a male) were placed in four experimental conditions (CB, CNB, TB and TNB), corresponding to interactions between environmental and social factors (n = 10 groups for each condition). Of the 40 groups only one initiated reproduction during the 18 weeks of cohabitation. Subsequently, animals were separated and isolated for 1 month and then paired with unfamiliar partners. Reproduction was monitored for an additional month, and 24 out of 39 females reproduced. In addition, of eight reproducing pairs placed in C conditions and 10 reproducing pairs maintained in T conditions, all but one pair continued reproduction. It was concluded that the delay in reproduction observed in autumnal individuals was the result of the social effects of living in groups as opposed to the environmental conditions of winter.

Short-term contact elicits heterospecific behavioral discrimination of individual odors in mound-building mice (Mus spicilegus).

The authors used a habituation-dishabituation procedure to test the ability of male mound-building mice (Mus spicilegus) to discriminate individual odors from males of another species of mouse. Male mound-building mice failed to spontaneously discriminate individual odors from Mus musculus musculus males, a natural competitor. After 24-hr contact with a male of one of the M. musculus subspecies (M. m. musculus or M. m. domesticus), experienced M. spicilegus males discriminated the individual odors of unfamiliar males of the same subspecies. These results confirm that discrimination of individual chemosignals is not confined to olfactory cues of a single species and provide new information about the effect of short-term contact on discrimination of individual odors across species.