ABSTRACT
This work aims to determine the most suitable nonlinear model to describe the growth of female collared peccaries (Pecari tajacu). The monthly records of the weight of 10 captive female collared peccaries over a period of two years in the Brazilian Amazon Region were used. The growth models used were the Von Bertalanffy, Brody, Gompertz and Logistic. The parameters were estimated by using the NLIN procedure from the SAS application. The criteria used to verify the adjustment of the models were: asymptotic standard deviation (ASD); coefficient of determination (R²); average absolute residual deviation (ARD) and the asymptotic rate (AR). The Brody model and the Logistic model estimated the highest (19.44kg) and the lowest (19.18kg) asymptotic weight (A), indicating the lowest (0.0070kg/day) and the highest (0.0121kg/day) maturation rate (K). These results and the coefficients of phenotypic correlation that varied from -0.75 and -0.47 confirmed the antagonistic nature between these parameters. The Brody model estimated the lower value for ARD, a limiting factor for describing the lowest value for AR through this model. The Brody model showed the best adjustment for AR, although the other models also showed a suitable adjustment to the weight data of said species/gender. Based on the AR obtained in this work, the Brody model is recommended for adjusting the growth curve of the female collared peccaries. Depending on the estimated values, especially for K, this trait can be included in a selection index.
Com o objetivo de ajustar modelos não-lineares, foram utilizados registros mensais do peso de 10 fêmeas de cateto (Pecari tajacu) coletados durante dois anos, no criatório do campo experimental Álvaro Adolfo da Embrapa Amazônia Oriental, Belém, PA. Utilizaram-se os modelos de Von Bertalanffy, Brody, Gompertz e Logístico. Os parâmetros foram estimados usando o procedimento NLIN do aplicativo SAS. Os critérios utilizados para verificar o ajuste dos modelos foram: desvio padrão assintótico (ASD); coeficiente de determinação (R²); desvio médio absoluto dos resíduos (ARD) e o índice assintótico (AR). Os modelos Brody e Logístico estimaram, respectivamente, o maior (19,44kg) e o menor (19,18kg) peso assintótico (A), caracterizando a menor (0,0064kg/dia) e a maior (0,0113kg/dia) taxa de maturação (K), haja vista a natureza antagônica entre estes parâmetros, comprovada pela correlação fenotípica variando entre -0,75 à -0,47. O modelo Brody estimou o menor valor para o ARD, fator limitante para caracterizar o menor valor para o AR por este modelo. Considerando o AR, o modelo Brody apresentou o melhor ajuste, contudo, pelos valores encontrados, os demais modelos também apresentaram ajuste adequando aos dados ponderais da referida espécie/sexo. Com base no AR adotado neste trabalho, recomenda-se o modelo Brody para ajustar a curva de crescimento de fêmeas de cateto (Pecari tajacu). Em razão dos valores estimados, sobretudo, para a K, essa característica pode ser incluída em um índice de seleção. Contudo, estudos com grupos mais representativos e criados em outras condições se faz oportuno.
Subject(s)
Animals , Growth/physiology , Swine/classificationABSTRACT
The fact that sexual segregation can occur in wild ruminants independently of sex-related differences in habitat use suggests that it results at least partly from social mechanisms. One of the simplest mechanisms which can be hypothesised is that individuals avoid the congener classes which frequently try to interact with them (be these interactions 'agonistic' or 'sexual', since courtship behaviour components typically induce withdrawal when performed outside the rut). The aim of the present study was to test, in mouflon sheep (Ovis gmelini), whether the age-sex classes which exchange frequent interactions on meeting occur rarely inside the same groups. Observations were made during winter, on a small population in Germany. Interactions were recorded at an attractive site where all age-sex classes met daily. Foot transects were conducted in parallel over the whole study area in order to determine group composition. As expected, adults of different sexes exchanged frequent interactions at the attractive site and were rarely found in the same groups under free-ranging conditions, while adult females, who interacted little with one another, were quite frequently associated. However, adult males simultaneously exhibited the highest rate of interaction at the attractive site and the highest frequency of association under free-ranging conditions. Unlike female-female and male-female pairs, in which interactions with a clear initiator and a clear recipient predominated, male-male pairs exchanged often spectacular but 'symmetrical' interactions (during which the two individuals behaved in the same way). The hypothesis that sexual segregation results from the avoidance of the congener classes which frequently engage interactions only holds for females. Adult rams interact frequently and seek companions with whom symmetrical interactions can be performed.
ABSTRACT
Our study of mouflon (Ovis musimon) rams in the Caroux-Espinouse massif (southern France) shows that several forms of philopatry occur. Some of the rams were sedentary, as were the ewes, up to the age of four years. Most of the rams, however, started to enlarge their home range from the age of two years. Rams of intermediate age visited their birth ranges during various periods of the year, whereas the adult males returned only during the rut. As potential mates were present on the home ranges of most of the dispersive males, it is difficult to interpret this process merely in terms of adaptation. We propose, instead, a psycho-ethological explanation, whereby the physiological disturbances intervening during the rut alter the significance of the range, the ram having to update the whole set of its sensory-motor past. This interpretation suggests that the animal has no representation of any pre-defined place, nor of any fixed aim. Rams would be able to reduce the imbalances they experience by creating a type of behaviour driven by a self-referential process, where spatial investment would outweigh any other evaluation, as an adaptative cost related to a possible inbreeding. This approach leads to reconsider the importance of spatial investment in animal's cognition and generally speaking the way an animal relates to its environment.
ABSTRACT
We analysed individual associations between mouflon (Ovis orientalis musimon) observed during one year in order to find ontogenetic patterns underlying the social structure of the population. A correspondence factorial analysis was performed on Simpson's coefficients to compare association profiles. No strong association was found between adults but some of the young adult females maintained a preferential bond with their mother until the age of three. Yearling males were firstly unstable in their social relations and subsequently developed a strong preference for peers (the preferred companion(s) of young adult males were always young adult males). Animals did not prefer to associate with other individuals of their own family (Wilcoxon test: n = 53; z = 0.463; a < 0.01). Localized abundant food sources caused large regroupings during spring. This was the only case where we noted a series of observations where the same unrelated animals were seen together. With the exception of the mother-offspring relationship, individual social preferences were based on the sex and age of the partner rather than on identity. The existence of social behaviour profiles dependent on sex and age is proposed to explain the above results.
