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Interactions between possums feeding on pasture in the observation area were rarely observed, other than the alert posture (see definition in methods section). There were no physical contacts seen between possums feeding in the area, and only 2 instances noted during other observations. On many occasions possums fed on pasture within 2 m of each other with no apparent interaction. Similarly, two, or occasionally 3, possums were commonly seen in the same tree and no interactions observed. However, possums around their dens or on frequently used tracks were not observed continuously for long periods (more than 30-60 seconds). There are likely to be more interactions in these areas. When in observing in these areas sounds associated with agonistic interactions between possums were frequently heard (screeches and nasal grunting sounds), but were never heard from possums feeding on pasture.

The most common social interaction seen was assumption of the alert posture. While grazing possums regularly sat back on their hindlegs and tail, and raised their body to an upright position (the alert posture). The fore paws were generally crossed at the carpus and the animal tended to look in a particular direction. There is seldom a scan of the area around the possum as is seen with meerkats or gophers. The possum generally returned to grazing within 5-15 seconds. Occasionally a possum rapidly dropped to all fours and moved away, usually to feed in a new location. When several possums were feeding in the area an alert posture movement by an individual did not seem to affect the others - generally they continued feeding. Loud sounds (possums screeching or plovers squawking) occasionally caused 1 or 2 possums to be alerted, but not others. There was little apparent pattern to the behaviour. Some animals fed for 25 minutes without stopping, and then assumed the posture 5-6 times over the next 2-3 minutes; others stopped and assumed the alert posture as often as every 40-80 seconds. Such ‘nervous’ possums seldom stayed in the observation area for more than 10 minutes.

The greatest number of possums in the area occurred in October and November 1991 when adults and many back-riding joeys were in the area. More than 22 individual animals (mothers and joeys) were seen during scans and one count had 12 animals (including joeys) in a 15 m2 area. On other occasions, 5-8 possums were seen feeding in a commonly used grazing area under a group of trees with no discernible interactions.

3.3.2.4.1. Descriptions of interactions seen

During the night of 31st March 1992, several possums fed on the pasture through until the early hours of the morning. They were generally widely scattered, except for 2 large animals which had

fed to within 5 m of each other. One of them frequently assumed the alert posture whereas the second fed for long periods between alert posture movements. At one stage, the first possum moved to within 2 m of the largest tree in the observation area and sniffed the ground over which the second had grazed 4-5 minutes previously; the second possum at this stage was about 5 m away. The first possum then humped its back, lowered its hindquarters, and rapidly brushed its tail sideways back and forth across the ground. This action was repeated 3 times over 20 seconds, and then the possum moved to within 2 m of the other animal and resumed feeding. Fifty-five seconds later the second possum, who had continued feeding throughout and at this time was facing away from the first, abruptly turned and chased that possum. Both ran towards the large tree and leaped 1-2 m up the trunk, though on opposite sides. The first possum dropped to the ground 20 seconds later, and was immediately chased back up the tree by the second who suddenly appeared around the base of the tree. This possum did not climb the tree, but moved 10-12 m away and resumed feeding. The first possum remained 5-6 m up the tree on a branch for another 8 minutes before climbing down and moving out of the observation area in the opposite direction to the second. The 3 other possums within 20m of this interaction continued feeding throughout.

During April 1992 the intact carcase of a possum was placed at the base of the only tree in the observation area which I had observed to be regularly climbed. Observation of the area around the carcase were made from 2000-0100 hrs the following night. In all, 8 possums approached within 5m of the carcase as they fed, with 3 of these animals distinctly sitting and gazing at it from 2-3 m away. A ninth possum approached the tree from behind and therefore it could not see the carcase (all others had been able to see the body from several metres away). As it rounded the base of the tree it immediately sat back in a bipedal threat posture with paw out. After slowly moving up to the carcase and sniffing up the length of its tail, the possum turned to the tree, reached up about 0.5m and marked it with the sternal gland twice and then began grazing. At this point another possum who had previously ignored the carcase approached from 2-3 m away, sniffed the tail, and then resumed grazing.

November 1991 saw the largest number of interactions observed, primarily because of the number of possums in the study area. On 2 nights, systematic observations from the hide were replaced by observations of groups of possums in a small area. Activities other than feeding behaviour were followed and recorded. Weather conditions were drizzly and cool with light cloud after heavy rain over the previous 2 days. Females were carrying back young and there were some independent juveniles about. Spring mating activity was probably occurring in the study area (R. Jackson pers.comm.). Seven avoidance interactions were seen between adult animals, none of which developed into a fight or involved vocalisations (observer 35 m away). The first indication of an interaction occurring was a variation in an individuals normal feeding pattern. The possum moved more rapidly for 10-15 m, and changed direction frequently. This animal was followed by another, and within 45-180 seconds (in 7 cases involving 3 different pairs of animals) the first possum turned and adopted a threat posture, and swiped at the other with its paw. In 2 cases the threat alone caused

the other to retreat; in 3 the following possum moved away after several swipes; and 2 interactions repeated the follow-the-leader, threat and swipe sequence before both animals resumed feeding. There were a number of trees both within the observation area and many on its periphery but only the latter were consistently climbed by possums. Three trees standing apart from others were often grazed around although seldom climbed, whereas possums were frequently seen feeding in kanukas around the edges of the area in trees apparently no different from those within the observation area. A light placed in one tree early in the project was investigated by several possums over 2 nights, and yet the tree was only noted as being climbed by 2 animals over the next 18 months.

The most extensive use of a tree in the observation area was made by a mother and joey in November 1992. After grazing for 1½ to 2 hours with the joey on her back the female slowly climbed a tree in the left region of the observation area and remained sitting in the fork of a branch for over 2 hours. The tree was climbed again the next night. A mother came through the netting fence and, as she went through the gap, dislodged her joey. The joey ran after her and attempted to return to her back. After pairing up again the mother fed in a small area for 35 minutes before the joey dismounted and began to feed independently. The joey slowly moved across the area keeping close to the mother until it was at the base of a tree. It sat at the base, flicking its tail for 20-30 seconds. The young possum then leaped 0.5m up the trunk and scrambled up another 1-2m before dropping back to the ground 20 seconds later. It then backed away from the tree and repeated the manoeuvre, this time climbing 3 m up the tree in a circular fashion. Two more repeats of the procedure were made before the joey moved away from the tree and began grazing, by this time 12-15 m from its mother. Once again there was no reaction from the other 4-5 possums in a 20-30 m area around the tree. The joey eventually rejoined its mother 35-40 minutes later. Eleven mother-joey pairs were closely observed with many more watched less intensively. The behaviour of the mothers during this time was no different from that during the rest of the year except the contact distance between animals was much smaller due to the joeys feeding close to them. Seventy-five percent of the back-riding joeys left their mothers' backs to feed on pasture for some time but remained in close contact - as the females moved towards the edge of the pasture the joeys climbed onto their backs.

Interactions between possums feeding on pasture were infrequent but were more common along the bush-pasture margin, particularly where possum runs came out of the bush. No fighting was seen but pairs of possums were frequently seen gazing at each other, often with one of the animals on the top of a fencepost. Short chases regularly followed, with the chased animal often escaping up a tree. One possible mating attempt was seen in May 1991, and was the most violent of all interactions witnessed. A large grey possum was seen chasing a smaller, darker, animal. The chaser came up close behind and attempted to knock the other over, and then mount it. The first twisted clear, making no noise, and ran off at which stage both became aware of my presence and disappeared.