The early hunting dog from Dmanisi with comments on the social behaviour in Canidae and hominins.

The renowned site of Dmanisi in Georgia, southern Caucasus (ca. 1.8 Ma) yielded the earliest direct evidence of hominin presence out of Africa. In this paper, we report on the first record of a large-sized canid from this site, namely dentognathic remains, referable to a young adult individual that displays hypercarnivorous features (e.g., the reduction of the m1 metaconid and entoconid) that allow us to include these specimens in the hypodigm of the late Early Pleistocene species Canis (Xenocyon) lycaonoides. Much fossil evidence suggests that this species was a cooperative pack-hunter that, unlike other large-sized canids, was capable of social care toward kin and non-kin members of its group. This rather derived hypercarnivorous canid, which has an East Asian origin, shows one of its earliest records at Dmanisi in the Caucasus, at the gates of Europe. Interestingly, its dispersal from Asia to Europe and Africa followed a parallel route to that of hominins, but in the opposite direction. Hominins and hunting dogs, both recorded in Dmanisi at the beginning of their dispersal across the Old World, are the only two Early Pleistocene mammal species with proved altruistic behaviour towards their group members, an issue discussed over more than one century in evolutionary biology.

Little brainiacs and big dummies: Are we selecting for stupid, stout, or small dogs?

Background: Brain size has been associated with intelligence of various orders and families of animals, leading to the concept of encephalization. Brain size scales with body weight between species within mammals to approximately the 0.67 power. However, within species, this scaling exponent appears to be much smaller (approximately 0.27 power). Aim: We examined whether this relationship has persisted in dogs over the 120 years since this was originally observed. Methods: Comparative cross-sectional study of magnetic resonance imaging (MRI) data obtained from 127 dogs, compared to historical data from 157 dogs and 24 non-dog canid species. Results: Brain size in dogs measured by MRI had a scaling exponent virtually identical to that observed previously (0.24 vs. 0.26). However, the proportionality constant was smaller, suggesting that dogs in the study cohort had relatively smaller brains than the historical cohort. Absolute brain size appeared to have both a lower and upper limit in dogs. When compared to non-dogs canids, the most appropriate "representative" size for a "typical dog" when examining allometric scaling across Canidae appeared to be approximately 10-15 kg. Conclusions: We interpreted the slight reduction in relative brain size to be a function of increased obesity in the study cohort compared to dogs examined 120 years ago. Further, we suggest that dog brains have a finite lower size limit. Finally, concepts of encephalization should not be applied to dogs.

How to Model Optimal Group Size in Social Carnivores.

AbstractModels of optimal group size need to identify the currency that correctly captures the fitness consequences of foraging. Although daily intake or daily net energy gain per animal are widely used as currencies, they are not ideal. They predict that all available time should be spent hunting and do not reflect performance during a hunt. We argue that the net rate while hunting is a better currency. Using an example based on the African wild dog, we illustrate the difference between maximizing daily net energy and net rate. Using the same example, we show that if foraging is limited by constraints on energy expenditure, then the optimal group size can be different from the size that maximizes the net rate while hunting. The direction of the effect depends on whether costs increase or decrease with group size. Furthermore, the proportion of time spent resting can be predicted. We suggest two novel approaches for future models: to consider the optimal hunting group size given a fixed group size and to investigate how the presence of dependent young may affect foraging behavior. We hope this will lead to meaningful conclusions on the role cooperative hunting has played in the evolution of sociality in social carnivores.

Metacognition in canids: A comparison of dogs (Canis familiaris) and dingoes (Canis dingo).

Metacognition refers to the ability to monitor one's own mental states. In the current study, we investigate whether domesticated dogs (Canis familiaris) and nondomesticated dingoes (Canis dingo) demonstrate metacognition by seeking information to remedy their own ignorance. In 2 studies, we used a naturalistic information-seeking paradigm in which subjects observed a human experimenter hiding a food reward behind an apparatus. Subjects could seek information by looking through a central window-like section of the apparatus to see where the reward was hidden. In Study 1, we tested whether dogs and dingoes were willing to seek information when interacting with the apparatus, finding that both species readily sought information when it was available to them. Study 2 provided a direct test of whether dogs and dingoes would seek information to rectify their own ignorance. We found evidence that both dogs and dingoes sought out information and were more likely do so when they did not already know where the treat was hidden. These results provide additional evidence suggesting that domesticated dogs seek information in the face of ignorance, as well as the first evidence of similar behavior in a nondomesticated canid. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

The bark, the howl and the bark-howl: Identity cues in dingoes' multicomponent calls.

Dingoes (genus Canis) produce a stereotyped bark-howl vocalisation, which is a unimodal complex signal formed by the concatenation of two call types (a bark and a howl). Bark-howls may function as alarm signals, although there has been no empirical investigation of this vocalisation's structure or function. We quantified the content and efficacy of the bark and howl segments separately and when combined, using 140 calls from 10 individuals. We found that both segments are individually distinctive, although howl segments are more accurately classified, suggesting a higher level of individuality. Furthermore, howls convey signature characteristics that are conserved across different contexts of production, and thus may act as 'identity signals'. The individual distinctiveness of full bark-howls increases above that of isolated segments, which may be a result of selection on improved signal discriminability. Propagation tests revealed that bark-howls are best described as medium-range signals, with both segments potentially allowing for individual discrimination up to 200m regardless of environmental conditions. We discuss our findings regarding the fitness benefits of encoding identity cues in a potential alarm call and propose additional hypotheses for the function(s) of bark and howl segments.

Environmental Enrichment Effect on Fecal Glucocorticoid Metabolites and Captive Maned Wolf (Chrysocyon brachyurus) Behavior.

Environmental enrichment is a technique that may reduce the stress of nonhuman animals in captivity. Stress may interfere with normal behavioral expression and affect cognitive decision making. Noninvasive hormonal studies can provide important information about the stress statuses of animals. This study evaluated the effectiveness of different environmental enrichment treatments in the diminution of fecal glucocorticoid metabolites (stress indicators) of three captive maned wolves (Chrysocyon brachyurus). Correlations of the fecal glucocorticoid metabolite levels with expressed behaviors were also determined. Results showed that environmental enrichment reduced fecal glucocorticoid metabolite levels. Furthermore, interspecific and foraging enrichment items were most effective in reducing stress in two of the three wolves. No definite pattern was found between behavioral and physiological responses to stress. In conclusion, these behavioral and physiological data showed that maned wolves responded positively from an animal well being perspective to the enrichment items presented.

Space use as an indicator of enclosure appropriateness in African wild dogs (Lycaon pictus).

A clear understanding of space use is required to more fully understand biological requirements of nonhuman animals in zoos, aid the design of exhibits, and maximize the animals' welfare. This study used electivity indexes to assess space use of two packs of African wild dogs (Lycaon pictus) and the appropriateness of two naturalistic, outdoor enclosures at the San Diego Zoo and Bronx Zoo. The results identified enclosure features that were both underutilized and overutilized. They suggest that replacing underutilized areas with features similar to areas that were overutilized may provide more preferred opportunities for the animals. Assessing space use of animals in human care may serve as an indicator of enclosure appropriateness and could have welfare implications. By looking at the possible reasons for area preferences, animal managers can get an idea of where improvements could be made. Designing future exhibits accordingly thus can provide possible welfare benefits for the animals concerned.

Dingoes (Canis dingo) can use human social cues to locate hidden food.

There is contention concerning the role that domestication plays in the responsiveness of canids to human social cues, with most studies investigating abilities of recognized domestic dog breeds or wolves. Valuable insight regarding the evolution of social communication with humans might be gained by investigating Australian dingoes, which have an early history of domestication, but have been free-ranging in Australia for approximately 3500-5000 years. Seven 'pure' dingoes were tested outdoors by a familiar experimenter using the object-choice paradigm to determine whether they could follow nine human communicative gestures previously tested with domestic dogs and captive wolves. Dingoes passed all cues significantly above control, including the "benchmark" momentary distal pointing, with the exception of gaze only, gaze and point, and pointing from the incorrect location. Dingo performance appears to lie somewhere between wolves and dogs, which suggests that domestication may have played a role in their ability to comprehend human gestures.

The effects of husbandry training on stereotypic pacing in captive African wild dogs (Lycaon pictus).

To examine the effects of operant conditioning on stereotypic pacing in 3 female African wild dogs located at the Franklin Park Zoo in Boston, this study made recordings of pacing behavior immediately following individual sessions of husbandry training and 2 no-training conditions. The study found significant differences in the percentage of observations spent in stereotypic pacing behaviors for all 3 dogs among the 3 different conditions. The authors discuss the data in terms of the contribution of motivated tasks to the effects and the role of food deprivation in the expression of stereotypic pacing. The study suggests that even short periods of training may improve the African wild dogs' welfare by reducing stereotypic pacing following the conditioning sessions.

The father(to)child affiliative bond: convergent evolution with the canid analogue.

Primate homologues, especially from the African great apes, can usually be successfully utilized to form comparisons with the human condition. However, the man(to)child pair-bond is not paralleled by any terrestrial primate nor even many mammals. Hence, knowledge of primate behavior would not be predictive of the pan-human social father. It is suggested that female choices of mating partners shifted in the direction of a canid analogue in that men's motivations to share resources with the female and to exhibit paternalistic behaviors were positively selected. Accordingly, it is argued that, for humans, convergent evolution occurred which trended toward the canid template. Consequently, it would be predicted that, compared to other terrestrial primates, the neuro-hormonal basis for the mother-child affiliative bond would be similar, but the basis for man(to)child affiliative bond would be dissimilar.