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Synanthropic populations of Mastomys natalensis (A. Smith, 1834) were studied in southeastern Sénégal in order to evaluate some elements of their social structure. Analysis of trapping data consisting in single and multiple captures indicates that adult males were less likely to be involved in multiple captures than any other cate­gory of individuals. Sex-ratio in adults was significantly female-biased, and multiple captures involving 4 individuals or more (up to 13) were characterized by the small number of adult males involved (usually one per capture). Dyadic encounters between males revealed a higher rate of aggressive behaviours in M. natalensis than in its sibling species M. huberti. These observations suggest that these synanthropic populations are subdivided in polygynous units in which: (1) a part of males are evicted from the social group before their maturity and (2) adult males of different social units display aggressive behaviour towards each other.
The terrestrial small mammal community of the Zakouma National Park (Chad) was assessed by live trapping in various habitats during the dry season. Nearly 3000 trap-nights yielded 505 captures of nine rodent and two shrew species, making up a representative small mammal community for the Sudanian savanna biotic zone. Murine rodents of the genus Mastomys dominated, with M. erythroleucus and M. cf. kollman- nspergeri occuring at similar abundances. The former was widespread and especially abundant in habitats with high tree cover. The latter was more localized, predominantly in annually flooded habitats characterized by a clay-rich soil, often with Acacia seyal as the main vegetation. Population structure differed between the two species, suggesting distinct reproductive strategies possibly linked with habitat preferences: the M. erythroleucus population comprised mainly young, immature individuals, whereas M. cf. kollmannspergeri was represented by older individuals, a significant fraction of which had already reproduced. Taterillus congicus and Tatera kempi (gerbilline rodents), togetjier with Lemniscomys zebra, were mainly found in more open habitats with sand-rich soils. Arvicanthis niloticus, Acomys cf. johannis, Mus mattheyi and Xerus erythropus were the other rodents captured, whereas shrews were represented by Crocidura fulvastra and Suncus sp.
Calomys venustus showed a cyclic seasonal pattern of reproductive activity characterized by a period of repose and a variable length of the period of sexual activity between August—September to May—June. The study was done from 1983 to 1999. During this time the population density increased from October—November to the end of autumn and sharply decreased in winter. Three peaks in rate of pregnancy were recognized in the breeding period: spring, summer and late summer. The average litter size was different among the three peaks in rate of pregnancy. The reproductive pattern had a peak at the beginning of the spring produced by overwintering animals, and another peak in summer-autumn caused by the reproductive activity of young born in the same period in which they breed. The spring cohort exhibited the greatest breeding contribution suggesting that this cohort is principally responsible for the yearly peak in abundance.
Five species of nematode were collected from the digestive tracts of 10 Coccymys ruemmleri from Papua New Guinea. Montistrongylus giluwensis sp. nov. can be distinguished from its congener by its size, in having more ridges in the synlophe, longer spicules and the form of the cuticle on the female posterior end. Syphacia (S.) coccymyos can be distinguished from all other species in the subgenus by having a laterally extended dorso-ventrally constricted oval cephalic plate and both cervical and lateral alae, together with the combination spicule length and egg size. The helminth assemblage had similar species richness to that of Chiruromys vates with Odilia mackerrasae the only species in common.
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