Heterothermy as the Norm, Homeothermy as the Exception: Variable Torpor Patterns in the South American Marsupial Monito del Monte (Dromiciops gliroides).

Hibernation (i.e., multiday torpor) is considered an adaptive strategy of mammals to face seasonal environmental challenges such as food, cold, and/or water shortage. It has been considered functionally different from daily torpor, a physiological strategy to cope with unpredictable environments. However, recent studies have shown large variability in patterns of hibernation and daily torpor ("heterothermic responses"), especially in species from tropical and subtropical regions. The arboreal marsupial "monito del monte" (Dromiciops gliroides) is the last living representative of the order Microbiotheria and is known to express both short torpor episodes and also multiday torpor depending on environmental conditions. However, only limited laboratory experiments have documented these patterns in D. gliroides. Here, we combined laboratory and field experiments to characterize the heterothermic responses in this marsupial at extreme temperatures. We used intraperitoneal data loggers and simultaneous measurement of ambient and body temperatures (T A and T B, respectively) for analyzing variations in the thermal differential, in active and torpid animals. We also explored how this differential was affected by environmental variables (T A, natural photoperiod changes, food availability, and body mass changes), using mixed-effects generalized linear models. Our results suggest that: (1) individuals express short bouts of torpor, independently of T A and even during the reproductive period; (2) seasonal torpor also occurs in D. gliroides, with a maximum bout duration of 5 days and a mean defended T B of 3.6 ± 0.9°C (one individual controlled T B at 0.09°C, at sub-freezing T A); (3) the best model explaining torpor occurrence (Akaike information criteria weight = 0.59) discarded all predictor variables except for photoperiod and a photoperiod by food interaction. Altogether, these results confirm that this marsupial expresses a dynamic form of torpor that progresses from short torpor to hibernation as daylength shortens. These data add to a growing body of evidence characterizing tropical and sub-tropical heterothermy as a form of opportunistic torpor, expressed as daily or seasonal torpor depending on environmental conditions.

Infection with Borrelia chilensis in Ixodes stilesi ticks collected from Pudu puda deer.

Lyme borreliosis is a vector-borne zoonosis caused by Borrelia burgdorferi sensu lato species complex spirochetes, which are maintained in transmission cycles among vertebrates and Ixodes ticks. Recently, a new genospecies within this complex, Borrelia chilensis, was described in Ixodes stilesi collected from the environment and from rodents in Chile. This tick also infests the native Southern pudu deer (Pudu puda). The objectives of this study were to investigate the prevalence, intensity of infestation, and aggregation of hard ticks on this deer species, and to determine the presence of borrelial pathogens in the ticks. Sixty-six deer were examined over a two-year period. A total of 179 ticks of two species, I. stilesi and Ixodes taglei, were collected. Of those, 100 were adults, 78 were nymphs, and one was a larva. Ixodes stilesi was the most prevalent tick (47%) and was highly aggregated (D=0.77) on the deer. Deer body weight was positively associated with tick burden. Borrelia spirochetes were detected in two (6.45%) of the examined I. stilesi ticks. Phylogenetic analyses of 16S and flaB gene sequences positioned these samples in the same clade with Borrelia chilensis VA1 previously described from Chile. These findings suggest that I. stilesi may play a role in the local persistence of B. chilensis. Further studies are required to fully understand the mechanisms of natural transmission of B. chilensis and the risk of infection in humans.

Sarcoptic Mange in a South American Gray Fox (Chilla Fox; Lycalopex griseus ), Chile.

Mange, a prevalent disease of dogs in Chile, is also a serious threat to wildlife. We report a case of sarcoptic mange in a South American gray fox or chilla fox ( Lycalopex griseus ). Further research is needed to understand the impact of mange in wildlife populations.