A Comparative study on the biology of two subspecies of tree squirrels, Paraxerus palliatus tongensis, Roberts, 1931 and Paraxerus palliatus ornatus (Gray, 1864) in Zululand

Abstract

In comparing the biology of the two subspecies of tree squirrels of P. palliatus, it was found that mass and all body measurements differ significantly. The subspecies of palliatus on the Mozambique plain occur in forested islands with lighter and smaller squirrels in dry forests and darker and heavier squirrels in more moist forest.Aspects of the other two southern African tree squirrels, Praxerus cepapi and Funisciurus congicus congicus have been included to further investigate adaptations to niche. The two subspecies of P- palliatus occur in forests that are in more moist regions whereas cepapi and congicus inhabitat relatively dry savanna regions and are subjected to greater extremes of temperature. Vegetation density presents the most obstruction to visibility in the forests of tongensis. Phenological observations show a seasonal pattern in all four the habitats. and of male tongensis it was 4,33 ± 1,34 (n=3). Home range of male ornatus was 3,18 ± 1,72 (n=12) Female home ranges were smaller for both ornatus and tongensis and averaged 2,19 ± 0,93 (n=6) and 0,73 ± 0,10 (n=3) respectively. Population density and biomass estimates were the highest for ornatus at 4,32 squirrels I ha or a biomass of 1 650 g /ha. Twenty-eight feeding records for each of the two subspecies of P. palliatus are included. A study of the feeding efficiency of the tree Paraxerus spp. indicate that ornatus is the most efficient feeder: on medium- and large- sized kernels it feeds in 59,5% to 66,7% of the time cf. tongensis and in 36,7% to 41,4% of the time cf. cepapi. Lengths of the different sections of the intestines, indicate that southern African tree squirrels are more insectivorous than tropical tree squirrels. Oxygen consumption indicates that the two forest species are adapted to more moist habitat than the two savanna species. Cepapi with the lowest oxygen consumption is particularly well-adapted to conserve energy. On the other hand, thermal conductance is the highest in congicus to rid it of excess heat. This is the only one of the four species which carries its tail over its head, probably thus aiding in thermoregulation. In captivity the forest species were found to be more active (move over greater distance per day) than cepapi and congicus. This is probably related to the dispersed food resources and the greater volume and range of movement in forests. Less allogrooming is performed by the forest than by the savanna ("contact") species. Frequencies of both murmuring and tail flicking were greater for the forest species than for the savanna species. Both these aspects are related to intraspecific communication in dense habitat. Sonographic analyses were made for almost all the calls of all four species. The main difference between the forest and savanna species is that the fundamental frequencies are consistently higher in the latter two species. The call of extreme alarm is a low-pitched bark in the forest species, but a high-pitched whistle in the savanna species. Between ornatus and tongensis the difference lies in frequency of vocalisation, the former being more vocal. Oestrus$ is communicated vocally in cepapi but olfactorily in ornatus and tongensis in the denser habitats. Reproduction in the two forest species is seasonal and occurs from about August to March. Murmuring by males is also seasonal and ceases when scrotal size diminishes. Gestation period is 59 din ornatus (n=l) and litter size is 1,69 + 0,48 in tongensis (n=13), and 1,60 ± 0,52 (n=10) in ornatus. The small litter size and long gestation is accompanied by a more precocial state of development at birth than and independence at almost half the age of temperate tree squirrel species. A description of moult of ornatus and tongensis is included, as well as the identification of ecto- and endoparasites collected from P. palliatus in KwaZulu.