A study measuring 19 parameters of otter tracks on three substratums snow, sand and limono-argileous mud was conducted in summer at the Otter Reintroduction Centre, Hunawihr, France. The eight breeding enclosures at the centre allowed precise measurement of the tracks of nine individuals five males and four females. Tubs containing the substratum material were dug into strategic sites used by the otters, such as along a fence or near a holt.
The tubs were kept moist. One hundred and twenty-eight tracks were measured. Due to the significant differences observed, therefore, only data for back feet, measured on mud, were used in the present analysis as these data represented over half For each individual analysis we obtained a classification function based on the formula:.
The discriminant analysis showed that dimensions were significantly different between substratums, particularly for 2 individuals 3 years old female: Unfortunately, lack of time and resources meant that it was not possible to prolong the test to obtain higher numbers of tracks for each substratum. It is planned, however, to repeat the test over a longer period, with the collaboration of other parks, to obtain more conclusive results. Despite the short duration of this preliminary study, there are some suggestions that care should be taken to note the substratum type when tracks are evaluated.
Otters like many mammals, exhibit sexual dimorphism so their tracks can be distinguished.
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The marked differences in body weights, when males are larger than females, have repercussions on the dimensions of tracks. The discriminant analysis demonstrates and chooses seven of the 19 parameters, which are sufficient to distinguish males from females.
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Not Enabled Word Wise: Enabled Amazon Best Sellers Rank: Amazon Music Stream millions of songs. Amazon Advertising Find, attract, and engage customers. Amazon Drive Cloud storage from Amazon. The rate of social transmission per unit network connection, relative to the baseline rate of asocial learning, was estimated to be A comparison of the support based on Akaike weight for different social learning models and the asocial learning model.
Italicized variables indicate the models with most support. This simply means it is plausible that all individuals learned by social transmission, except the innovator. However, an ad hoc visual examination revealed that the spread of task solutions through the otter group seemed to follow the association network more closely in task types 1—4 than 5—6 figure 4 ; supplementary video 1 [ 41 ] shows a task 5 trial. In task types 5—6 this pattern was no longer apparent figure 4. Furthermore, fitting a model without social transmission to the solving-order data for tasks 5 and 6 improved Akaike's information criterion corrected for small sample size by 4.
The order of solving in the smooth-coated otters for each of the six tasks. Offspring are plotted as circles and parents as triangles. The individual that solved the task at each part of the sequence is plotted in red and joined with red lines. The dashed blue line shows the path we would expect the red line to take if there were no social transmission but allowing that juveniles are faster to solve. If there is social transmission through the network the red line should be above the blue line.
In a — d tasks 1—4, the individual to solve the task next tends to be an offspring with a relatively high level of association to informed otters relative to others for that solve, and the red line is clearly above the dashed blue line.
IUCN Otter Specialist Group
In e — f tasks 5—6, this pattern is no longer apparent. The social transmission model with most support was multiplicative rather than additive The parents only solved 1 out of 6 tasks father and 3 out of 6 tasks mother , compared with the offspring solving an average of 5. Given the stronger support for the multiplicative model table 1 , this indicates that young otters learned faster how to solve tasks both socially and asocially when compared with their parents.
Support total Akaike weight and estimates for the effects of sex and age. The ratios of effects are taken from a combined OADA model for both species, including social transmission, sex and age, all of which were allowed to differ between species. Fewer than half of the otters solved task 4 figure 2 ; electronic supplementary material, table S3; supplementary video 3 [ 41 ] , suggesting that this was indeed the most complex task.
NBDA TADA confirmed that tasks 3 and 4 were more difficult slower to solve than tasks 1 and 2 expected time to solve relative to task 1: The individuals in the three Asian short-clawed otter groups appear to have learned the solutions to the four novel foraging task types individually rather than socially: Together, these results suggest that Asian short-clawed otters are unlikely to have relied on social information to solve the novel foraging tasks.
Across all tasks presented to each species, Asian short-clawed otters were estimated to use social information in a maximum of However, because some of the tasks presented to each species were different, we re-ran analyses using only the tasks presented to both. When including only the three tasks that required the same actions to be solved smooth-coated otters: When the screw-top task was also excluded from the analysis because a clear container was used for the Asian short-clawed otters figure 2: In all cases, the estimated effect of social transmission was thus much stronger for smooth-coated otters.
Therefore, overall our results strongly suggest that social transmission was less likely to be an important factor in the spread of task solutions in Asian short-clawed otters than in smooth-coated otters, but replication in a larger number of otter groups of both species presented with a larger battery of identical tasks is needed to confirm this finding.
Although males and females differed in task-solving rates only in Asian short-clawed otters, there is only weak support for a meaningful species difference: This indicates that we cannot exclude the possibility that the two species showed the same sex difference in solving rates.
However, there was reasonable evidence that the relative age difference in task-solving rates, with young otters solving significantly faster than their parents, was stronger in smooth-coated otters than in Asian short-clawed otters 7. A caveat here is that the offspring in the smooth-coated otter group were 1—2 years old, while the offspring in the Asian short-clawed otter groups were 4—10 years old.
Whether younger Asian short-clawed otter offspring would have outperformed their parents as observed in the smooth-coated otters thus remains to be investigated. Social learning has been studied in many species, but never in otters, even though many otter species are likely to be capable of social learning given their gregarious nature, and knowledge of their social learning strategies may help inform reintroduction programmes to support these vulnerable species.
The aim of our study was threefold: We tested two species of otter that live in family groups but differ in life-history traits as well as diet. Given their gregarious nature, we predicted that both species may show evidence of social learning. However, we made no predictions concerning species differences or the adoption of particular social learning strategies, given the exploratory nature of this study and the fact that no one has studied social learning in otters before.
We show for the first time that smooth-coated otters can learn from each other how to solve novel foraging tasks, while we found no support for this in the Asian short-clawed otters. These results are based on only a few captive groups. Our findings regarding otter species and age differences in social learning tendencies should thus be interpreted with caution and would benefit from replication on a larger captive sample and validation in wild populations.
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Nonetheless, our results offer a first insight into the social learning abilities of the subfamily Lutrinae. Furthermore, our results make ecological sense if we consider what is known about the natural foraging habits of these species: However, their natural prey does not necessitate extensive extractive foraging behaviour to consume. In our experimental setting, it thus makes sense that the smooth-coated otters would be naturally inclined to watch each other for foraging information, especially as they are unlikely to have adapted to deal with complex extractive foraging tasks.
In contrast, the Asian short-clawed otters are not known to forage in groups, and their natural diet consists mainly of prey i. They may, therefore, have less of a natural tendency to turn to each other when facing novel food puzzles that are somewhat similar to the prey they encounter in the wild. However, virtually no information is available on the development of extractive foraging behaviours in Asian short-clawed otters and the extent to which these are socially learned in the wild. Field studies have provided extensive evidence for juveniles' reliance on social learning to acquire extractive foraging behaviours in other mammal species, including black rats [ 45 ], meerkats [ 13 ] and chimpanzees [ 12 ].
We have just acquired access to breeding populations of Asian short-clawed otters and additional populations of smooth-coated otters and hope to determine in the near future a to what extent newborn pups use social information across development to acquire their extractive foraging skills and b whether we can replicate or reject our preliminary finding of a species difference in reliance on social learning between smooth-coated and Asian short-clawed otters. In the smooth-coated otters, the order in which we presented the tasks was confounded with task difficulty because we did not initially intend to address this question at the time of experimental design , such that the last two tasks to be presented also appeared to be the most difficult ones.
Post hoc analyses actually showed that the order in which the otters solved the tasks followed the social network more closely for the first four tasks than for the latter two, and for the latter two a model including only asocial learning i.
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However, the result may instead be due to the otters having gained sufficient experience with the previous four tasks that by the end of the experimental period they no longer relied on each other to solve them. To address these concerns, we counterbalanced the task order across the groups of Asian short-clawed otters, but again found no support for social transmission in this species, even for the most difficult task that fewer than half of the otters managed to solve.
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Even then, our results may be consistent with the strategic use of social learning in smooth-coated otters. Further work might aim to investigate whether this strategy operates in otters. We found no such patterns in the Asian short-clawed otters. Again, further work is needed to be certain that this is a general difference between the species across a larger number of groups, as we cannot exclude the possibility that the adults and young in the single smooth-coated otter group we studied happened to differ in unrelated factors e.
Nonetheless, this apparent species difference in social learning strategies makes sense if we consider species differences in life-history traits: This extended juvenile period in the family group in smooth-coated otters is likely correlated with an extended period for socially acquiring essential skills for survival.
However, as noted above, it is important to consider again here that the youngest Asian short-clawed otter tested was already four years old, and the oldest offspring was ten. Furthermore, Asian short-clawed otters are known to have group-coordinated anti-predator behaviour [ 28 ].
It may well be that this species would show evidence for social transmission in tasks that tested the transmission of anti-predator behaviour against a novel stimulus [ 49 — 51 ] rather than foraging behaviour. Our findings that smooth-coated otters are capable of learning from each other how to exploit novel food sources, and that there may be species differences in otters' reliance on social transmission, may have important conservation implications.
Conservation organizations facilitating reintroduction programmes could benefit from using social transmission as a way of training captive-bred otters to cope with life in the wild. Previous research suggests that animals trained on important life skills e. For example, young smooth-coated otters' training before release into the wild may benefit from sibling demonstrators performing survival skills, as we found that the novel foraging task solutions spread most efficiently between peers horizontal transmission rather than from parents to offspring vertical transmission.
Furthermore, in some species, such as possibly the smooth-coated otter, older individuals may not be able to acquire new foraging skills as easily as younger otters, perhaps making them unsuitable for reintroduction programmes as their ability to adapt to their new environment and hence their survival chances may be limited. Finally, we found no direct evidence for the otters' reliance on social learning to depend on assumed foraging task complexity.
However, future studies could present various types of appropriate live prey not normally provided in captivity e. In conclusion, this first exploration of social learning in otters shows that this taxon merits further study, not only because the wide range of life-history traits represented across the various species can provide further insights into the evolution of social learning strategies, but also because conservation efforts may be facilitated by an increased understanding of these species' ability to adapt to change through social transmission.
All authors gave final approval for publication. National Center for Biotechnology Information , U. R Soc Open Sci. Published online Aug Author information Article notes Copyright and License information Disclaimer. Electronic supplementary material is available online at https: Received May 10; Accepted Aug 2.