Use of the sun as a heading indicator when caching and recovering in a wild rodent.

A number of diurnal species have been shown to use directional information from the sun to orientate. The use of the sun in this way has been suggested to occur in either a time-dependent (relying on specific positional information) or a time-compensated manner (a compass that adjusts itself over time with the shifts in the sun's position). However, some interplay may occur between the two where a species could also use the sun in a time-limited way, whereby animals acquire certain information about the change of position, but do not show full compensational abilities. We tested whether Cape ground squirrels (Xerus inauris) use the sun as an orientation marker to provide information for caching and recovery. This species is a social sciurid that inhabits arid, sparsely vegetated habitats in Southern Africa, where the sun is nearly always visible during the diurnal period. Due to the lack of obvious landmarks, we predicted that they might use positional cues from the sun in the sky as a reference point when caching and recovering food items. We provide evidence that Cape ground squirrels use information from the sun's position while caching and reuse this information in a time-limited way when recovering these caches.

Caching in the presence of competitors: Are Cape ground squirrels (Xerus inauris) sensitive to audience attentiveness?

When social animals cache food close to their burrow, the potential for an audience member to observe the event is significantly increased. As a consequence, in order to reduce theft it may be advantageous for animals to be sensitive to certain audience cues, such as whether they are attentive or not to the cache event. In this study, observations were made on three groups of Cape ground squirrels (Xerus inauris) in their natural habitat when they cached provisioned food items. When individuals cached within 10 m of conspecifics, we recorded the attentiveness (i.e. whether any audience members were orientated towards the cacher, had direct line of site and were not engaged in other activities) and identity of audience members. Overall, there was a preference to cache when audience members were inattentive rather than attentive. Additionally, we found rank effects related to cache avoidance whereby high-ranked individuals showed less avoidance to cache when audience members were attentive compared to medium- and low-ranked individuals. We suggest this audience sensitivity may have evolved in response to the difference in competitive ability amongst the ranks in how successful individuals are at winning foraging competitions. This study demonstrates that Cape ground squirrels have the ability to not only monitor the presence or absence of conspecifics but also discriminate individuals on the basis of their attentive state.

Identification of learning mechanisms in a wild meerkat population.

Vigorous debates as to the evolutionary origins of culture remain unresolved due to an absence of methods for identifying learning mechanisms in natural populations. While laboratory experiments on captive animals have revealed evidence for a number of mechanisms, these may not necessarily reflect the processes typically operating in nature. We developed a novel method that allows social and asocial learning mechanisms to be determined in animal groups from the patterns of interaction with, and solving of, a task. We deployed it to analyse learning in groups of wild meerkats (Suricata suricatta) presented with a novel foraging apparatus. We identify nine separate learning processes underlying the meerkats' foraging behaviour, in each case precisely quantifying their strength and duration, including local enhancement, emulation, and a hitherto unrecognized form of social learning, which we term 'observational perseverance'. Our analysis suggests a key factor underlying the stability of behavioural traditions is a high ratio of specific to generalized social learning effects. The approach has widespread potential as an ecologically valid tool to investigate learning mechanisms in natural groups of animals, including humans.

Inbreeding and inbreeding depression of early life traits in a cooperative mammal.

Mating between relatives often results in negative fitness consequences or inbreeding depression. However, the expression of inbreeding in populations of wild cooperative mammals and the effects of environmental, maternal and social factors on inbreeding depression in these systems are currently not well understood. This study uses pedigree-based inbreeding coefficients from a long-term study of meerkats (Suricata suricatta) in South Africa to reveal that 44% of the population have detectably non-zero (F > 0) inbreeding coefficients. 15% of these inbred individuals were the result of moderate inbreeding (F ≥ 0.125), although such inbreeding events almost solely occurred when mating individuals had no prior experience of each other. Inbreeding depression was evident for a range of traits: pup mass at emergence from the natal burrow, hind-foot length, growth until independence and juvenile survival. However, we found no evidence of significant inbreeding depression for skull and forearm length or for pup survival. This research provides a rare investigation into inbreeding in a cooperative mammal, revealing high levels of inbreeding, considerable negative consequences and complex interactions with the social environment.

Multi-generational persistence of traditions in neighbouring meerkat groups.

Reports of socially transmitted traditions based on behavioural differences between geographically separated groups of conspecifics are contentious because they cannot exclude genetic or environmental causes. Here, we report persistent differences between neighbouring groups of meerkats (Suricata suricatta) where extensive gene flow precludes genetic differentiation. Over 11 years, some groups consistently emerged later from their sleeping burrows in the morning than others, despite complete turnovers in group membership and the influx of immigrants. Group territories overlapped and, in many cases, the same sleeping burrows were used by different groups. Differences persisted even after accounting for effects of group size, weather and burrow characteristics, and were unrelated to food availability within territories. These results provide compelling evidence that the emergence times of meerkat groups represent conservative traditions.