The behavioural biology and management of southern hairy-nosed wombats (Lasiorhinus latifrons) in captivity

The southern hairy-nosed wombat (Lasiorhinus latifrons) suffers a range of problems in captivity, including reproductive failure, stereotypical behaviour, aggression and obesity. A population of captive L. latifrons was studied to examine welfare in captivity, and where relevant, conclusions were extrapolated to the conservation of wild L. latifrons populations, and the critically-endangered northern hairy-nosed wombat (Lasiorhinus krefftii). Six experiments were undertaken, which examined sound perception, investigated faeces as a communication tool, refined methods of faecal hormone metabolite analysis, investigated how group size and enclosure size affect behaviour and welfare, and determined changes in body temperature and corticosterone with season and environment. Lateralised responses to auditory stimuli provide insight into the perception and welfare of animals. When bilaterally presented with sounds of varying biological significance (predator, food-conditioned and neutral), wombats were able to differentiate stimuli, as evidenced by changes in exploration, grooming and vigilance behaviour during the post-sound period. Head turn direction did not differ between sounds, but wombats’ significant left side bias pre-sound (mean 58% left head turns, CI 49-66%) shifted to right side bias post-sound (mean 43% left head turns, CI 40-45%; P = 0.001). Thus laterality was evident in response to a sound stimulus, although side biases were not altered by sound type. Intraspecific communication in wombats includes chemical signals found in faeces, such as pheromones. Wombats presented with four faeces types (dingo, male and female wombats and plastic control) responded differently to each, indicating odour differentiation, and were most reactive to faeces from animals that posed the greatest threats (male wombat and dingo). Wombats approached the dingo faeces 5.6 times per treatment period, compared with the control (3.0 times; P = 0.004) and female wombat faeces (3.7 times; P = 0.049). They also avoided other wombats most when male wombat faeces were present (8.3 retreats/period) compared to the control (4.5; P = 0.02), or female wombat (4.3; P = 0.01). All faeces caused more hiding behaviour (% time, pre-treatment: 71.3, treatment: 75.6, post-treatment: 72.7; P < 0.05) and reduced grazing time (min/period, pre-treatment: 15.8, treatment: 6.9, post-treatment: 13.1; P = 0.0002) and walking (min/period, pre-treatment: 85.2, treatment: 66.9, post-treatment: 78.2; P = 0.01), indicating an increased perception of risk. It was concluded that wombats use chemical signals in biological markers to gain information about the level of risk from predators and unfamiliar conspecifics. Faecal hormone metabolite analysis is a non-invasive measure of stress and reproductive hormone patterns. Two potential limitations of this technique were investigated, storage delay effects and within-sample variation, for corticosterone, progesterone and testosterone metabolites using enzyme immuno-assay. Within-sample variation was low (< 15 % of total variance), when three sampling sites per sample were compared. However, storage delays reduced progesterone from 51 to 44 ng/g from 0 to 72 hours (P = 0.05), increased testosterone over the first 6 hours from 8.4 – 11.2 ng/g (P = 0.01), and initially increased corticosterone from 65.5 – 80.3 ng/g by 6 hours (P = 0.001), with a subsequent return to original concentrations. Thus immediate storage is desirable, although testing from multiple sample sites was unnecessary. Faecal sampling and internal temperature loggers were used to determine how wombat physiology was affected by ambient conditions in captivity. Core body temperature was measured hourly over a 6 month period from winter to summer and faecal corticosterone metabolite concentrations were measured every three days during August and January. Body temperature had distinct nychthemeral and seasonal patterns, peaking at night and in winter. Faceal corticosterone secretion was highest in summer, the season of low food availability within their natural range, and was negatively correlated with ambient temperature in both winter and summer (r72 = -0.33, P < 0.0001 and r94 = -0.27, P = 0.01 respectively). In the wild, wombats are essentially solitary but may share burrows. Zoos have imposed social structures, which have not been investigated for impact on behavior and welfare. Wombats in large (L, 1♂:3♀) and medium (M, 1♂:2♀) sized groups had reduced vigilance behaviour (such as visual scanning) compared with small (S, 1♂:1♀) groups (count/day: L: 55, M: 69, S: 115, P = 0.002). Vigilance decreased as the distance between wombats decreased (air smelling: r8698 = 0.23, P < 0.0001; visual scanning: r8698 = 0.27, P < 0.0001; object smelling: r8698 = 0.33, P < 0.0001). This pattern has previously been observed in mainly social species hence it was of interest that the largely solitary L. latifrons wombats also adjusted vigilance levels with group size in accordance with the theory of reduced predation risk in larger group sizes. Inadequate space availability has been linked to abnormal behaviour and poor breeding success in many captive species. However, despite the prevalence of these issues with captive wombats, the effects of space availability are undetermined. Wombats in small enclosures (S, 75.5 m2) did more visual scanning than those in medium (M, 151 m2) or large (L, 224 m2) enclosures (count/day: S: 52.8; M: 33.9; L: 28.8, P < 0.001), more biting (count/day: S: 1.96; M: 0.42; L: 0.28, P = 0.01), more retreating from other wombats (count/day: S: 15.0; M: 9.9; L: 7.1, P = 0.03), and more digging on the fence line, apparently to escape (min/m/day: S: 0.78; M: 0.16; L: 0.24, P < 0.0001). Thus small enclosures negatively impacted on wombat welfare. The welfare of L. latifrons wombats in captivity is therefore a complex yet important issue, and this research could be utilized to improve their conditions in captivity.