César Ades

Asymmetry of Leg Use During Prey Handling in the Spider Scytodes globula (Scytodidae)

In spitting spiders Scytodes globula collected in the field, anterior leg loss was more frequent on the left than on the right side, possibly as an outcome of predatory episodes. A laboratory study was performed in which intact adult females of S. globula were placed with individuals from three species of recluse spiders, Loxosceles intermedia, L. gaucho, and L. laeta. The frequency of probing touches by spitting spiders to their prey was significantly higher with left leg I than with right leg I. Left leg II and right leg II also differed in touching frequency, but in a less marked way. The results, which may represent the first evidence of behavioral laterality in a spider species, suggest that behavioral asymmetry may be an ancient evolutionary trait.

Isolation induced changes in Guinea Pig Cavia porcellus pup distress whistles

Guinea Pig Cavia porcellus pups emit high-pitched distress whistles when separated from their mother. In order to assess the influence of the duration of a brief isolation period on whistle acoustic structure, we recorded the distress whistles of six 8-day old pups separated for 15 min from their group in a novel environment and compared the mean values of the first and last 30 whistle notes. Acoustic analysis revealed, throughout the session, a significant decrease in whistle duration, an increase in mean frequency and a tendency for a decrease in number of harmonics in the first part of the note. Results demonstrate that, throughout a brief isolation period, the vocal response of Guinea Pig pups to isolation undergoes structural changes possibly related to time-dependent changes in motivational state.

Long-distance calls in Neotropical primates

Long-distance calls are widespread among primates. Several studies concentrate on such calls in just one or in few species, while few studies have treated more general trends within the order. The common features that usually characterize these vocalizations are related to long-distance propagation of sounds. The proposed functions of primate long-distance calls can be divided into extragroup and intragroup ones. Extragroup functions relate to mate defense, mate attraction or resource defense, while intragroup functions involve group coordination or alarm. Among Neotropical primates, several species perform long-distance calls that seem more related to intragroup coordination, markedly in atelines. Callitrichids present long-distance calls that are employed both in intragroup coordination and intergroup contests or spacing. Examples of extragroup directed long-distance calls are the duets of titi monkeys and the roars and barks of howler monkeys. Considerable complexity and gradation exist in the long-distance call repertoires of some Neotropical primates, and female long-distance calls are probably more important in non-duetting species than usually thought. Future research must focus on larger trends in the evolution of primate long-distance calls, including the phylogeny of calling repertoires and the relationships between form and function in these signals.

A dog at the keyboard: using arbitrary signs to communicate requests

As a consequence of domestication, dogs have a special readiness for communication with humans. We here investigate whether a dog might be able to acquire and consistently produce a set of arbitrary signs in her communication with humans, as was demonstrated in “linguistic” individuals of several species. A female mongrel dog was submitted to a training schedule in which, after basic command training and after acquiring the verbal labels of rewarding objects or activities, she learned to ask for such objects or activities by selecting lexigrams and pressing keys on a keyboard. Systematic records taken during spontaneous interaction with one of the experimenters showed that lexigrams were used in an appropriate, intentional way, in accordance with the immediate motivational context. The dog only utilized the keyboard in the experimenter’s presence and gazed to him more frequently after key pressing than before, an indication that lexigram use did have communicative content. Results suggest that dogs may be able to learn a conventional system of signs associated to specific objects and activities, functionally analogous to spontaneous soliciting behaviors and point to the potential fruitfulness of the keyboard/lexigram procedure for studying dog communication and cognition. This is the first report to systematically analyze the learning of arbitrary sign production in dogs.

Two-Item Sentence Comprehension by a Dog (Canis familiaris)

Syntax use by non-human animals remains a controversial issue. We present here evidence that a dog may respond to verbal requests composed of two independent terms, one referring to an object and the other to an action to be performed relative to the object. A female mongrel dog, Sofia, was initially trained to respond to action (point and fetch) and object (ball, key, stick, bottle and bear) terms which were then presented as simultaneous, combinatorial requests (e.g. ball fetch, stick point). Sofia successfully responded to object-action requests presented as single sentences, and was able to flexibly generalize her performance across different contexts. These results provide empirical evidence that dogs are able to extract the information contained in complex messages and to integrate it in directed performance, an ability which is shared with other linguistically trained animals and may represent a forerunner of syntactic functioning.

An analysis of travel costs on transport of load and nest building in golden hamster

We investigated the effects of travel costs on transporting nest material and nest-building activity in golden hamsters. Nest-deprived animals were submitted to run alleys 30, 90 and 180 cm long to access a source containing paper strips as nest material (Experiment 1) or were submitted to the same travel costs in 24-h experimental sessions (Experiment 2). We noted that increased travel costs were related to a decreased number of trips to the source, larger amounts (cm(2)) of nest material transported per trip (although total loads also decreased in longer alleys), longer intervals between trips, and increased time spent at the source and in nest building activity. Foraging efficiency (i.e. size of load divided by the time spent at the source) decreased as a function of travel costs, and animals transported their loads in two fundamental ways: in 30-cm alleys, they simply used their mouth to pull the paper strips, but in 90- or 180-cm alleys they transported the loads in their cheek pouches. The animals were faster when returning to the home-cage and their running speed (cm/s) increased as a function of the length of the alley, showing that animals are under different environmental pressures when searching for resources and subsequently running back with the load to the nest. Both male and female subjects were sensitive to travel costs, but males engaged in nest building activity more promptly and exhibited higher mean performances in most measures. We conclude that nest material is a good reinforcer, and our major results are in accordance with the predictions of microeconomic and optimal foraging theories.

Are dogs able to communicate with their owners about a desirable food in a referential and intentional way

The ability of dogs to use human communicative signals has been exhaustively studied. However, few studies have focused on the production of communicative signals by dogs. The current study investigated if dogs are able to communicate by using directional signals towards some desirable object in the environment and also if they show an apparent intention to manipulate their owner’s behavior in order to receive it. Some operational criteria were used to investigate referential and intentional communication: the signal should be influenced by the audience and by the recipient’s direction of visual attention; the sender should display gaze alternations between the recipient and the object and attention-getting behaviors, and, finally, the sender should persist and elaborate the communication when attempts to manipulate the recipient failed. Aiming to investigate these criteria in dogs, 29 subjects were tested using an experimental set up in which they could see a desirable but unreachable food and they needed the cooperation of their owners in order to receive it. This study found evidence of all operational criteria, especially for gaze alternation between the owner and the food, which suggested that some dogs’ communicative behaviors could be functionally referential and intentional. Nevertheless, similar to other studies about social cognition in animals, it is not possible to distinguish if the dog’s behaviors are based on simple mechanisms or on a theory of mind about their owners.

Vocal sequential exchanges and intragroup spacing in the Northern Muriqui Brachyteles arachnoides hypoxanthus

Sequential exchanges of vocalizations (staccatos and neighs) emitted by Northern Muriquis Brachyteles arachnoides hypoxanthus were recorded at the Biological Station of Caratinga, Minas Gerais State, Brazil. Staccatos and neighs containing larger proportion of short elements were preferentially produced during short-range exchanges; neighs, produced by a larger number of participants, were typical of long-range exchanges. Staccatos emitted by animals feeding in a dispersed manner contained a larger proportion of tonal elements than those emitted by muriquis feeding in a cohesive manner. Sequential exchanges seem thus to be constituted by two inter-related subsystems of calls that aid muriquis to coordinate intragroup spacing, despite the poor visibility of the habitat.

Comparison of two methods for glucocorticoid evaluation in maned wolves

Analysis of faecal glucocorticoid metabolites provides a powerful noninvasive tool for monitoring adrenocortical activity in wild animals. However, differences regarding the metabolism and excretion of these substances make a validation for each species and sex investigated obligatory. Although maned wolves (Chrysocyon brachyurus) are the biggest canids in South America, their behaviour and physiology are poorly known and they are at risk in the wild. Two methods for measuring glucocorticoid metabolites in maned wolves were validated: a radio- and an enzyme immunoassay. An ACTH challenge was used to demonstrate that changes in adrenal function are reflected in faecal glucocorticoid metabolites. Our results suggest that both methods enable a reliable assessment of stress hormones in maned wolves avoiding short-term rises in glucocorticoid concentrations due to handling and restraint. These methods can be used as a valuable tool in studies of stress and conservation in this wild species.

BIOACOUSTICS OF DOMESTICATION: ALARM AND COURTSHIP CALLS OF WILD AND DOMESTIC CAVIES

ABSTRACT Comparisons of wild (Cavia aperea) and domestic (C. porcellus) cavies promote an understanding of the physiological and behavioral effects of domestication. The richness and peculiarities of Cavia acoustic repertoires encourage the use of this model for testing how domestication alters repertoires and the physical structure of calls. We present a comparison between alarm and courtship calls of domestic and two populations of wild cavies from different geographic regions, one of them with a short-term captivity history of 25 generations. We found significant differences between domestic and wild cavies in both calls, particularly in temporal parameters, and only spectral differences between two wild populations in alarm calls. There were also differences in the frequency of emission of calls: alarm calls were more frequent in the wild and courtship calls were more frequent in the domestic species. Our results suggest that domestication has influenced the temporal parameters of both alarm and courtship calls of C. porcellus, but not the spectral parameters that, instead, may be influenced by environment or population factors.