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Copyright of African Journal of Ecology is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of African Journal of Ecology is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We studied the social system and time budget of kob antelopes in the Comoé National Park, Côte d'Ivoire from March 1993 till May 1998, a population that is suffering from heavy over-hunting, to assess information about the effects of population decrease and its relevance for conservation of this antelope population. Single animals accounted for the majority of observed kob antelopes. Time allocated to certain behavioural traits depended on group size, with animals in smaller units spending less time on behaviours sensitive to predation risk. Single animals allocated far less time to ruminating and feeding being more vigilant and walking more. Groups were highly fluid and associations between individuals could be predicted by home-range overlap among females but not for female/male associations where association indices might be influenced by reproductive aims. Frequency of social groupings did not change compared with earlier studies when population density was much higher. However, compared with these studies maximum group size decreased, and smaller groups became more abundant. The observed effect of group size on the time budget of kob antelopes in combination with a steady decrease in group size because of reduction in population size might have a severe impact on the long-term persistence of the studied kob population due to anticipated aggravated predation effects. As males form the majority of single animals, putting them on higher predation risk, number of males decreases more rapidly than the number of females, which might eventually lead to a collapse of the kob population. Résumé Nous avons étudié le système social et l'emploi du temps des antilopes cobes dans le Parc National de Comoé, en Côte d'Ivoire, entre mars 1993 et mai 1995. C'est une population qui souffre d'une grave sur-chasse, et nous voulions évaluer les informations sur les effets de la diminution de la population et leur pertinence par rapport à la conservation de cette population d'antilopes. La majorité des observations de cobes concernaient des animaux solitaires. Le temps consacréà différents types de comportement dépendait de la taille du groupe, les animaux faisant partie des plus petits groupes allouant moins de temps à des comportements sensibles au risque de prédation. Les animaux isolés passaient beaucoup moins de temps à ruminer et à se nourrir car ils étaient plus vigilants et se déplaçaient davantage. Les groupes étaient très fluides, et on pouvait prévoir les associations entre individus femelles par le recouvrement de l'occupation spatiale des femelles, mais pour les associations mâles-femelles, les indices peuvent être influencés par des buts reproducteurs. La fréquence des regroupements sociaux n'a pas changé par rapport aux études antérieures, quand la densité de la population était beaucoup plus élevée. Cependant, par rapport à ces études, la taille maximale du groupe a diminué, et les plus petits groupes sont plus abondants. L'effet observé de la taille du groupe sur le budget temporel des antilopes cobes, combinéà la diminution très nette de la taille des groupes due à la réduction de la taille de la population, pourrait avoir un impact sévère sur la persistance à long terme de la population étudiée car on peut s'attendre à des effets plus graves de la prédation. Comme les mâles forment la majorité des individus solitaires, ce qui les met plus en danger face aux prédateurs, le nombre de mâles diminue plus vite que celui des femelles, ce qui pourrait conduire à l'effondrement de la population de cobes. [ABSTRACT FROM AUTHOR]

The territorial system of kob antelopes in the Comoé National Park, Côte d’Ivoire, was studied from March 1993 until April 1997. Whereas size and shape of territories remained constant between 1993 and 1994, the number of territories decreased from 1994 onwards. A decline of the population density probably led to the decline in territory numbers and also to variations in size and shape of the remaining territories. The decline of kob numbers is the result of heavy poaching in the study area. Whereas a lekking system was present in the study area prior to 1975 when the population density was approximately 14.4 kobs/km2, males switched to the resource defence territorial system present today after the population density decreased to 12.5/km2 in 1993 and finally to 2.3/km2 in 1997. Compared to other research areas with higher population densities, territories in the Comoé National Park are larger, almost all adult males are capable to defend a territory, fights over territories are rare and loss of territory tenureship is almost exclusively due to the death of the territorial male. We suggest that those differences can all be related to the low population density in the study area. [ABSTRACT FROM AUTHOR]

Abstract The kob (Kobus kob kob ) population studied in the Comoé National Park, Ivory Coast, suffered unsustainable losses to poaching before and during the investigation. This in turn did not only lead to low densities but also changed the population composition, resulting in a strong female bias in all age classes except juveniles. The relative rarity of adult males probably had negative effects on the population recruitment. Although mating occurred throughout the year and birth intervals were short, at least in some females, annual birth-rate was low compared to earlier studies in the same area. Effective conservation measures are urgently needed to ensure the future existence of the studied population. [ABSTRACT FROM AUTHOR]

Abstract Spatial and temporal habitat use of kob antelopes (Kobus kob kob) have been investigated in the Comoé National Park (Ivory Coast, West Africa) by use of radio telemetry. A total of 23 kob were equipped with radio collars and radio tracked for up to 15 months. Home ranges of males were smaller and those of females larger than expected from theoretical models. Adult males used smaller areas than adult females and did not show seasonal home range shifts. Daily distances travelled did not differ between sexes. Kob walked less during the night than by day and covered shorter distances in the wet season. Whereas an increase in home range overlap between females resulted in higher rates of association among individuals, association of adults of mixed sexes was not correlated with the degree of home range overlap. Territorial behaviour of males and predator avoidance by females are suggested to explain the sex-specific differences in home range size of adults and the deviation from the predicted sizes. Predator avoidance is presumed as the main reason for the reduced walking distances at night as well as in the wet season. Reproductive behaviour and feeding ecology are assumed to determine the degree of association of conspecifics. [ABSTRACT FROM AUTHOR]