Jean Joachim

Artificial neural networks as a classification method in the behavioural sciences

The classification and recognition of individual characteristics and behaviours constitute a preliminary step and is an important objective in the behavioural sciences. Current statistical methods do not always give satisfactory results. To improve performance in this area, we present a methodology based on one of the principles of artificial neural networks: the backpropagation gradient. After summarizing the theoretical construction of the model, we describe how to parameterize a neural network using the example of the individual recognition of vocalizations of four fallow deer (Dama dama). With 100% recognition and 90% prediction success, the results are very promising.

Sarcoptes scabiei: Specific immune response to sarcoptic mange in the Iberian ibex Capra pyrenaica depends on previous exposure and sex.

Host acquired immunity is a critical factor that conditions the survival of parasites. Nevertheless, there is a shortage of data concerning inter-individual immunological inequalities in wild mammals. Sarcoptic mange is a widespread parasitosis that severely affects mammals such as the Iberian ibex (Capra pyrenaica). Despite some work on the subject, the immune response to sarcoptic mange infestation is still a complex and poorly understood phenomenon. To improve knowledge of the host-Sarcoptes immunological interaction, 18 Iberian ibexes were experimentally infested. IgG levels were assessed using ELISA to test for potential factors determining the specific immune response to infestation. Previous exposure and sex appeared to affect the IgG response to infestation and our results suggest a sex-biased immunomodulation. We discuss the immunological pattern of host-Sarcoptes interactions and also suggest further lines of work that may improve the understanding of immunological interactions of host-Sarcoptes systems.

Spectral acoustic structure of barking in roe deer (Capreolus capreolus). Sex-, age- and individual-related variations

In roe deer, barking is a loud call commonly given by males and females during inter- or intraspecific interactions. The analysis of a set of 19 spectral variables computed on 560 calls revealed significant variation between sexes, individuals, and probably age classes. Discriminant analysis predicted the sex of an individual with a 93.5% probability from a small portion of the bark frequency range. Among six males, a linear combination of six variables predicted the identity of the barking individual with a 70% probability. These sexual and individual differences provide the potential for social recognition from vocalizations. These results are consistent with the hypothesis that barking in roe deer may allow remote signalling of presence, location and identity, and play an important role in the territorial system of this species.

Individual variation in migratory and exploratory movements and habitat use by adult red deer (Cervus elaphus L.) in a mountainous temperate forest

Using data from a global positioning system (GPS), seven adult red deer (Cervus elaphus L.) were tracked in the Parc National des Cévennes, southern France, between November 1998 and December 2000 to assess the factors affecting large-range movement patterns and habitat use. The home range varied from a single compact area for females to three distinct seasonal ranges for males, which used alternative migratory strategies (i.e. non-, downward- and upward-migrants). The migrants used mainly southerly and easterly aspects, and wintered in areas having steeper slopes than were used during summer or the rut season. For males, the time of rut migration was mid-September and they finally entered wintering ranges from mid-December to the beginning of January. Exploratory behaviour (i.e. individuals found outside the limits of their familiar area but returning to it a few days later) occurred in both sexes and for all individuals monitored during at least a 6-month period. Velocity and efficiency of exploratory movements were higher than usual movements. During these exploratory movements, hinds may have used different landscape attributes (elevation, slope, canopy cover) while stags did not. These results provide new empirical information that could be used for building and applying broad-scale spatial and landscape use models in ecological research.

Diurnal and seasonal variations of roaring activity of farmed red deer stags

Various environmental and social parameters are known to affect the roaring activity of the red deer (Cervus elaphus) stags, but their influence is difficult to estimate in the field. We consequently studied the diurnal changes in roaring activity of three adult stags kept in separate paddocks with hinds over the course of a breeding season during seven 24 h field sessions. Roaring activity started at the end of September, peaked for all three stags in mid-October before ceasing abruptly about a week later. Both the hourly number of roar bouts and the hourly number of roars emitted differed between stags and sessions: the youngest (5-year-old) stag roared more at the beginning of the rut, while roaring of the two other stags (11- and 12-year-old) progressively increased over the season. However, at the peak, the roaring activity of the three stags was similar. During the two first weeks of October, the roaring activity of the two more vocal stags significantly decreased just before sunrise and at least 2.5 h after sunset, while it significantly increased during daytime. The implications of these results for estimating the population size of free ranging red deer based on roaring activity of stags are briefly discussed.

Estimating the occupancy rate of spatially rare or hard to detect species: a conditional approach.

We consider the problem of estimating the occupancy rate of a target species in a region divided in spatial units (called quadrats); this quantity being defined as the proportion of quadrats occupied by this species. We mainly focus on spatially rare or hard to detect species that are typically detected in very few quadrats, and for which estimating the occupancy rate (with an acceptable precision) is problematic. We develop a conditional approach for estimating the quantity of interest; we condition on the presence of the target species in the region of study. We show that conditioning makes identifiable the occurrence and detectability parameters, regardless of the number of visits made in the sampled quadrats. Compared with an unconditional approach, it proves to be complementary, in that this allows us to deal with biological questions that cannot be addressed by the former. Two Bayesian analyses of the data are performed: one is noninformative, and the other takes advantage of the fact that some prior information on detectability is available. It emerges that taking such a prior into account significantly improves the precision of the estimate when the target species has been detected in few quadrats and is known to be easily detectable.

The population size and distribution of the Vulnerable beira antelope Dorcatragus megalotis in Djibouti

The Vulnerable beira antelope Dorcatragus megalotis is endemic to the Horn of Africa and believed to occur in low numbers in Djibouti, in the southern mountain range of Aser-Jog. In the absence, however, of detailed information on the species, we censused the population and estimated its density, and collected data on the occurrence of potential competitors and predators. A total of 99 different individuals were sighted, with an estimated average density of 0.69 km -2 (range 0–1.25 km -2 ) over the 13 massifs comprising the mountain range. We did not locate the species in massifs located near villages, suggesting it is affected by human activities. One of the main threats to the beira may be competition for grazing with domestic goats. The creation of a wildlife refuge in Aser-Jog would increase the attractiveness of the area to tourists and encourage international organizations to support a conservation programme for the beira.

Impact of climatic variations on bird species occupancy rate in a southern European forest

Species that are affected by climatic variations can undergo modification in range and/or abundance. Knowing how individuals or species occupy their habitat is essential to understand how species use their environment, and detecting variations that might affect this use can be determinant in species management. Hierarchical modeling is regularly used to assess for occupancy rate (i.e. proportion of patches occupied in a region), particularly when it is required to consider detectability-related issues. The present study is the first application of the conditional model presented in Dupuis et al. (Biometrics 2010), which is applied in the case of a heterogeneous area that might be divided into homogeneous sub-areas. Their approach is used to study the impact of three consecutive particularly cold winters on a selected set of bird species in a forest of southern France in the context of available prior information on birds detectability. We examined a limited range of factors that might influence the response of some bird species to climate. We considered the case of sedentary, partially migrating and migrating species. We also assessed if the biogeographical origins of the different species affect their occupancy rates. Globally, changes in occupancy rates between 1985 and 1987 indicates for the first time a continentalization of the regional forest fauna, reflected by the expansion of Palearctic and Turkestano-European faunistic type species, with depletion or extinction of European, Turkestano-Mediterranean and Mediterranean sedentary species. We have also shown the importance of prior information.

Variations in bird communities of the Saharan mountains

Characteristics and variations of the bird communities in the Saharan mountains were evaluated in five massifs from West to East: the Adrar of Mauritania, the Ahaggar in Algeria, the Adrar of the Iforas in north-eastern Mali, the Aïr Mountains in northern Niger, and the Red Sea Mountains in the Eastern Desert of Egypt. Bird censuses (n = 110) were conducted during dry seasons. A total of 139 species were recorded, of which 120 remained after elimination of occasional visitors and were used for analysis. Total richness and diversity increased from the most central and high Ahaggar towards the western, eastern and especially southern massifs. Among the resident communities the number of Saharo-Sindian species was higher in the central, eastern and western massifs, whereas Afrotropical species were more abundant in the southern ones. A principal component analysis distinguished three opposite poles of species linked with Adrar of the Iforas, Aïr and Red Sea mountains and cluster analysis led to the ordination of the five massifs along a longitudinal gradient from West to East. Avifaunal variations between the different Saharan mountains sampled led to a regional pattern in relation with faunistic affinities and it fitted with the three biogeographical subregions of the Saharan biome: Sahara, Sahel and Nubian Desert.