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1. Methods

TRAPPING

Treeshrews were trapped with locally purchased cage traps of small poultry wire mesh, baited with a slice of ripe plantain or banana. Before a trapping session, traps were fixed open and prebaited with several hunks of banana once or twice at two- to three-day intervals. Prebaiting saved time by training the animals to come to trap sites, and I hoped it would also reduce trap-shyness by habituating treeshrews to being rewarded in traps without the stress of capture. Prebaiting brilliantly succeeded in the first goal, because most animals were captured the first day traps were set. There is no control data by which to judge the second objective. Toward the end of the study, we also used mixed concentrated banana and strawberry essence on a cotton swab placed in the trap, as an attractant (A. Rabinowitz pers. com.) along with banana. On the high plot at Poring we tried baiting with a mixture of peanut butter, oatmeal, fermented prawns (balachan), and dried beef shreds, in a fruitless attempt to capture the other montane treeshrew, Dendrogale melanura. In 1989 and 1990 traps were covered with fresh leaves to shelter the animals from sun and rain, but beginning in the rainy season in 1990 a plastic bag was tied with string over the top of each trap.

In 1989 and 1990 I set traps at nightfall (1700 h–1800 h) and left them open at night. In 1991 a population explosion of rats filled 50 percent of the traps each night. Thereafter, to avoid interference by rodents, for the first trapping day of the session I set traps before dawn, from 0430 to 0600 h, but then left them open the following night to monitor the rat populations. In 1989 we checked traps twice during the day, beginning at 0900 and 1700; but in 1990–91 I usually visited traps three times, beginning about 0800, 1400, and 1630 h. The octagonal wire mesh of the traps was large enough for treeshrews to poke their muzzles through, which could injure the skin on the rostrum. Incidence of damage

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from this injury increased with the amount of time animals stayed in the traps, and with the number of times they were recaptured during the same session. To minimize this problem, and generally reduce the risk of accidents, I trapped for only two days each session, after an initial four- or five-day session at each study site to capture as many individuals as possible. Two days were not long enough to capture all treeshrews in the area.

At the lowland, Eastern Ridge site at Poring (1989), traps were placed at 20 m intervals, on the nearest likely sites, in a 6 x 8 grid, with a 2 x 10 extension, designed to cover the available flat area of the ridge top. The area of the ridge top within the trails was 6 ha, that inside the trap array was 3 ha. The 1,000 m elevation, Langanan Ridge site, where T. montana was studied, had a wedge-shaped grid of 9 x 10 traps, tapering to 4, which again filled the flat space of about 4 ha on the ridge top. The home ranges of most species turned out to be so large that a grid arrangement on a practical scale for acquiring home range data from trapping was of little use (I had originally hoped to supplement radio-tracking by trapping), so at Danum Valley in 1990 I abandoned the grid pattern and

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arranged traps at 25 m intervals in two 500 m lines 100 m apart. At all times traps were placed on the nearest likely trapping spot to each station (fallen log, dense brush, treefall). At twenty-three places on the Eastern Ridge grid at Poring and at seven places on each line at Danum Valley, additional traps were tied up in vine tangles or on branches about 2–3 m above ground. These were put in likely spots, without reference to the other trap markers.

In 1989 we trapped the Eastern Ridge grid at Poring in the first weeks of April, May, and finally in mid-August; and Langanan Ridge at the beginning and end of July. We also ran a small altitudinal transect with 30 traps from 880 m to 1,000 m on Langanan Ridge for three days in June 1989. At Danum Valley we trapped each month toward the end of the month from September 1990 to September 1991, except February was missed, and March was trapped twice, at its beginning and end. In the January trapping period, a group of elephants went through the study area, systematically destroying man-made objects (rain gauges, signs, trail markers, etc.). They stomped on seven baited traps but interestingly did not step on one that contained a treeshrew, while flattening the two on each side (trapping in January was curtailed, and this month is excluded from most data). Trapping success was very high. At Danum the number of individual treeshrews captured per month ranged from nine to twenty-four (fig. A-I.1).

HANDLING TREESHREWS

Trapped animals were transferred to cloth bags, weighed, measured, and eartagged with numbered monel self-piercing tags. In addition, the tail hair was cut in a unique pattern for each individual, to aid visual recognition in the field (Kawamichi and Kawamichi 1979). The first treeshrew captured, a female T. tana, died of stress shock while being held gently (a problem also common in many tropical squirrel species). Thereafter, I anesthetized all treeshrews by injecting them with ketamine hydrochloride, through the holding bag, before initial handling and fitting of radio-collars. No other mortality ever occurred during handling. After handling, anesthetized animals were allowed to recover in a cloth bag and released on the next round of trap checking. If a treeshrew to be collared was caught at nightfall, I kept it overnight in the safety of my room and released it in the morning. Later in the study, I found that neither T. longipes, T. minor, nor T. montana were susceptible to shock, and these species were handled without anesthesia, except when collars were fitted. I was reluctant to anesthetize treeshrews repeatedly, so when animals were recaptured, I did not anesthetize them but usually weighed them in the bag, examined the reproductive condition of females, and released them without further handling.

PROBLEMS ENCOUNTERED

To help those who study treeshrews in the future, I briefly sketch the problems or failures with our methodology. The traps themselves caused a few injuries: one treeshrew died when the door fell on its neck; one caught its leg in the wire

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and broke it; two tore their skin badly on the protruding wire of the spring; and one caught its radio-collar in the bait hook. All injured treeshrews were immediately released without treatment or handling, and all survived the injuries and were recaptured with healed wounds in the following months, including the broken leg. In my experience from trapping many mammal species, injured animals survive far better when immediately released and left untreated in the wild than when sentimental humans attempt to “hospitalize” them. We made 420 treeshrew captures during the study, so the casualty rate from the trapping procedures was extremely low.

The use of ear tags was not a success, because many were lost. When treeshrews that had lost ear tags were recaptured, I permanently marked them by clipping a terminal toe phalange as is the standard method in mammalogy. This also was not successful because several individuals, especially T. longipes, then became trap-shy. One of these regularly came to bait sites, where he was repeatedly seen (he had a radio-collar), but he was never caught again during the remaining six months of the study. About a half dozen animals, mostly young, were recaptured without ear tags after several months, with tail hairs grown out, so that I lost their identities and thus lost valuable information on longevity and the dispersal of young. In future, I would use electronic numbers on transponders for permanent marking.

The radio-collars seemed to cause few problems in large species. One female T. tana whose collar was tight was recaptured in a state of shock, so her collar was removed. She was recaptured the next month in perfect condition and recollared with no problem. One male T. tana was found dead sixteen days after collaring. He may also have been stressed by the collar, but he was in good condition, robust and glossy, with no evident injury or external signs of stress. A number of collars slipped off because they were too loose.

Animals should not be released before full recovery from anesthesia. All three small species, but no large ones, had a tendency to get a forefoot caught between the collar and the neck. This happened especially when the animals were first collared and coming out of anesthesia (Ptilocercus particularly), when they probably tried to push the collar off. There may be no way to avoid this problem, but collars should be carefully fitted, and not too loose. Radios were always removed at the end of the study or tracking session, but several animals were recollared, or were trap-shy, and wore radios for six to twelve months without evidence of any injury from the collars.

The most trouble-free radio-collars for large species were those with a brass band enclosed in shrink-tubing that formed a closed loop antenna that was bolted on (Wildlife Materials, Inc.). I had an extra hole drilled on each side of the tuned diameter center so that fit could be adjusted. Whip antennas were tried, but these always broke off rapidly. Teflon fabric collars frayed and broke.

RADIO-TRACKING

The study areas were gridded with trails every 100 m and marked with meter marks every 20 m (Poring) or 25 m (Danum). Radio-tagged treeshrews were followed

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on foot on the study-area trail networks, and signals were triangulated from three trail marks approximately every 20 minutes. If the animal was moving rapidly, it was followed continuously, so that it would not escape from range. During a sample, the treeshrew was followed from before it emerged from its nest until after it retired.

Telemetry data was hand-plotted for best accuracy (some bad triangulations must always be discarded, and computers are not good at choosing the right data to reject). Distances moved and areas of ranges were measured from plotted maps with a digitizing tablet and DesignCad ¯ software.

Time only allowed each person/team to do intensive radio-tracking of 6 to 7 individual treeshrews per month for three-day samples, or 4 to 5 animals for fiveday samples. The chief drawback of the continuous following method is that few animals can be tracked in any month, and the necessity to follow treeshrews of both sexes of five species meant that often an individual was only followed for one sample. I tried to radio-collar all resident adults of every species except T. minor, where my object was to collar only contiguous females or both members of a pair. I gave priority to putting radios on males whose females had working radios, so that interactions could be monitored during tracking, but sometimes the timing of when individuals were captured, when radios functioned, and when we could schedule tracking did not work out, so that tracking of contiguous or overlapping individuals was staggered in time.