Preferencje help
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 17

Liczba wyników na stronie
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 1 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników

Wyniki wyszukiwania

Wyszukiwano:
w słowach kluczowych:  Sciuridae
help Sortuj według:

help Ogranicz wyniki do:
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 1 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników
We tested whether species-specific behavioral traits could explain patterns of habitat patch occupancy by five different squirrel species in Ontario, Canada: the northern and southern flying squirrel (Glaucomys sabrinus and Glaucomys volans), the North American red squirrel (Tamiasciurus hudsonicus), the eastern chipmunk (Tamias striatus), and the eastern gray squirrel (Sciurus carolinensis). Flying squirrel species exhibit group nesting in winter, which may put them at risk of extirpation in small patches with few individuals to contribute to group nests. Flying squirrels are also volant, potentially making non-treed matrix a barrier. Our surveys revealed that G. sabrinus was most likely to occur in large patches that were embedded in landscapes with low connectivity, and least likely to occur in small patches in highly connected landscapes. Conversely, G. volans was most likely to occur in large, well-connected patches and least likely to occur in small, unconnected patches. Patch occupancy by the cursorial squirrels was not strongly influenced by patch area or isolation. These findings reinforce previous studies suggesting that an understanding of species-specific traits such as behavior is an important consideration when interpreting habitat fragmentation effects.
Studies on the behaviour of grey squirrels Sciurus carolinensis Gmelin, 1788 and other species belonging to the same genus, suggest they exhibit dominance hierarchies among both males and females, and their mating strategy is promiscuous or polygynous, However, there is little information available on how dominance translates into repro­ductive success or on the levels of genetic variation or genetic substructuring within a population. To address these questions, we used multilocus DNA fingerprinting to quantify genetic diversity and estimate relatedness amongst individuals in a free­-ranging population of grey squirrels. Background band-sharing values revealed a high degree of genetic diversity existed. The frequency distribution of band-sharing values between known first order relatives and presumed unrelated animals was significantly different. Estimates of relatedness between individuals were therefore based on threshold levels of genetic similarity and used as a tool to infer close kinship. Possible kinship groups were identified using the spatial distribution of the home ranges of adults and juveniles. Levels of relatedness between neighbouring adults was low with five family units identified comprised of putative parents and their offspring. Several juveniles from the single cohort revealed levels of relatedness intermediate between first order relatives and unrelated animals, suggesting possible second order relationships (eg half siblings) existed. The implications of these relationships are discussed.
A total of 51 and 21 adults of Barbary ground squirrels (Atlantoxerus getulus) were trapped during May–July 2006 from the introduced populations on Fuerteventura Island (Canary Islands) and the native populations in Morocco, respectively. One trematode, 1 cestode and 4 nematode species were recovered belonging to five families: Brachylaima sp. (Brachylaimidae), Catenotaenia chabaudi (Catenotaeniidae), Protospirura muricola (Spiruridae), Dermatoxys getula and Syphacia pallaryi (Oxyuuridae), and Trichostrongylus sp. (Trichostrongylidae). We report for the first time the presence of P. muricola, Trichostrongylus sp. and Brachylaima sp. in A. getulus. Brachylaima sp. was found in the insular population only, as a result of a diet that includes snails. The two oxyurids were found at both sites. The continental population showed higher species richness (5 vs 3 species). This is the first report of helminth parasites from A. getulus from the Canary Islands.
The morphology of the lingual side of the mandible was analysed in the genus Marmota. Adults from 12 of 14 living species were compared using geometric morpho- metric techniques. The information on the lingual side was then combined with that of the labial side from a previous analysis. The combined dataset is the most complete description of a marmot mandible ever used in an interspecific comparison in this genus and it represents the second morphological study ever realized that includes a large sample with all marmot species. The study confirmed the uniqueness of M. vancouverensis for mandible morphology, with atypical traits likely to have evolved in a relatively young but small population of marmots isolated on the Vancouver Island since the end of the Pleistocene (10 000-100 000 ybp), stressing the importance of a strong effort to save this species from extinction. Marmota olympus also has a distinctive mandibular trait undetected in a previous analysis using information on the lingual side only. The Olympic marmot has a longer evolutionary history but it is presently found only in the Olympic Peninsula and shares with M. vancouverensis a similar history of geographic isolation and population bottlenecks. Genetic bottlenecks might have profoundly affected marmot morphological evolution and may have increased the rate of shape change in marmot radiations. Both the analysis of the lingual side alone and the combined dataset (lingual and labial information) failed to clearly discriminate the two main marmot subgenera but the combined description of the mandible supports the similarity of the two main species (M. caligata and M. flaviventris) of the subgenus Petromarmota, and the proximity of the North American M. monax to Palaearctic marmots. Surprisingly, the analysis of the lingual side indicated that M. camtschatica and M. marmota have unusual traits for the subgenus Marmota. At least for the latter species, this finding is congruent with peculiarities in fur and parasitic relationships, and may be related to an ancient phylogenetic origin for M. marmota.
Much is known of the ecology and behaviour of Spermophilus richardsonii (Sabine, 1822) (Richardson's Ground Squirrel), but little has been discussed of its anatomy. Here we document details of its cranial anatomy, based upon 95 specimens from a single locality, focusing primarily on previously undescribed features. This documentation provides the essential information for studying intra- and interpopulational variation in cranial characteristics in both quantitative and qualitative contexts. Skulls of S. richardsonii examined were generally uniform in structure, and no obvious sexual differences were observed.
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 1 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.