Tupai "ss1.37"

DISCUSSION OF HOME RANGE

The only other published home range data on treeshrews were collected by observation of marked Tupaia glis on Singapore (Kawamichi and Kawamichi 1979). This showed mean home range areas of 1.02 ha for males (N = 16) and 0.88 ha for females (N = 18). These are about eight times smaller than those of the comparable plain treeshrews in Sabah. Their “social” density, calculated in a way similar to mine (e.g., adults only), was 240 individuals/km² without young and up to 720 with young (Kawamichi and Kawamichi 1982). This correlates with the small home ranges. Langham (1982), in a trapping study of T. glis in peninsular Malaysia, also reported tremendously high densities of 369 and 478 treeshrews/km². Dans (1993) reported densities of Palawan treeshrews of 1.6 to 3.2 individuals/ha, in the same range as those of Bornean species. No other measurements of treeshrew ranging behavior have been reported.

West Malaysian T. glis thus reach numbers tenfold higher than those of T. longipes on my study areas in Sabah. In West Malaysia T. glis is the only terrestrial treeshrew, so one can ask whether T. longipes numbers in Sabah are depressed by competition with other species. Even the sum of the highest recorded densities of all three syntopic terrestrial species at Danum Valley, 96/km² (table 8.5) is much less than half of those reported for T. glis alone on the mainland. A likely alternative hypothesis is that food resources are more scarce and restrict population sizes on Borneo (see chap. 12).

Although there is little other information on daily ranging behavior with which to compare Bornean treeshrews to other congeners, it is instructive to compare the ranging behavior of treeshrews to that of other mammals. Primates are by far the best studied taxon in this regard, and the data for many genera and species have been summarized (Smuts et al. 1987). Because they are of a size similar to treeshrews and share some ecological features, squirrels (Emmons 1975, 1980; Payne 1979) and elephant shrews (Rathbun 1979) can be usefully compared (table 8.6).Data were collected in different ways by different investigators, and intraspecific variation is common, so species values should be viewed only as ballpark trends. Two features stand out in this small list: (1) for small primates the day range is small relative to home range size; and (2) with

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Table 8.6. Ranging behavior of other small, insectivorous/frugivorous equatorial rainforest taxa. Mean home ranges of males and females arboreal (A), terrestrial (T).
Species	Mass (g)	Home Range (ha)	Day Range (m)	Movement Rate (m/h)	Reference
Elephant Shrews (all T)
Rhynchocyon chrysopygus	540	1.7			Rathbun 1979
Elephantulus rufescens	58	0.34			Rathbun 1979
Squirels
Ratufa bicolor (A)	1442	3-7	315	30	Payne 1979
Callosciurus notatus (A)	227	<1			Payne 1979
Protoxerus stangeri (A)
2 subadult females)	488	4.1	572		Emmonos 1975
Epixerus ebii (T)	577	17.5	857	130	Emmonos 1975
helisciurus rufobrachium (A)	375	4.6	519	61	Emmonos 1975
Funisciurus pyrrhopus (T)	330	3.4	343	48	Emmonos 1975
Funisciurus lemniscatus (T)	139	1.2	393	47	Emmonos 1975
Primates (all A)
Cebuella pygmaea	115	0.4	290		Soini 1988
Aotus trivirgatus	800	9.2	708		Wright 1985
Callicebus moloch	800	6.9	671		Wright 1985
Saimiri sciureus	900	>250	1,500?		Terborgh 1983
Saguinus fuscicollis	400	30-100	1,140-1590		Goldizedn 1987
Galago alleni (females)	265	10			Charles-Dominique 1977
Galagoides demoidoff (females)	61	0.6-1.4			Charles-Dominique 1971
Tarsius spectrum	120	1			MacKinnon and MacKinnon 1980

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the exception of one terrestrial squirrel, the widest-ranging species are leapers and vertical-cling-and-leapers that eat many insects (but not all such species), including galagos, tamarins, and squirrel monkeys. In comparison, the salient character of the treeshrew daily ranging behavior in Sabah is that it is greater to much greater than that of most other species in the same weight range. Home ranges are also on the large end of the spectrum. In both home range and distances traveled, treeshrews resemble the most mobile of primates. Because feeding at fruit trees reduces daily path lengths in both treeshrews and tamarins (Terborgh 1983), long daily excursions are most likely due to either search for insects and/or search for undiscovered fruits or widely dispersed small fruit sources. The champion travelers, T. gracilis and T. longipes, exceed the largest daily distances of much bigger primates. In contrast, the arboreal lesser treeshrew has a home range exactly the same size as that of the lesser bushbaby (Galagoides demidoff) of the same weight.

The long daily path lengths of treeshrews go hand in hand with the extended active periods described in the previous chapter. To meet their daily needs, a long time spent moving translates into a long distance moved. Together these patterns are evidence that the food supply of Bornean treeshrews is highly dispersed, so that each animal needs a long daily time and distance to fulfill its basic needs.