Christopher E. Gordon

Keystone effects of an alien top-predator stem extinctions of native mammals

Alien predators can have catastrophic effects on ecosystems and are thought to be much more harmful to biodiversity than their native counterparts. However, trophic cascade theory and the mesopredator release hypothesis predict that the removal of top predators will result in the reorganization of trophic webs and loss of biodiversity. Using field data collected throughout arid Australia, we provide evidence that removal of an alien top-predator, the dingo, has cascading effects through lower trophic levels. Dingo removal was linked to increased activity of herbivores and an invasive mesopredator, the red fox (Vulpes vulpes), and to the loss of grass cover and native species of small mammals. Using species distribution data, we predict that reintroducing or maintaining dingo populations would produce a net benefit for the conservation of threatened native mammals across greater than 2.42 × 106 km2 of Australia. Our study provides evidence that an alien top predator can assume a keystone role and be beneficial for biodiversity conservation, and also that mammalian carnivores more generally can generate strong trophic cascades in terrestrial ecosystems.

What factors allow opportunistic nocturnal activity in a primarily diurnal desert lizard (Ctenotus pantherinus)

Most animals show strong 24-h patterns of activity, usually being diurnal or nocturnal. An Australian desert skink, Ctenotus pantherinus, is unusual in being active day and night when all other Ctenotus species are diurnal, making it an excellent model to explore factors that promote night-time activity. We tested whether C. pantherinus 1) selects cooler temperatures than diurnal skinks, 2) shows no difference in mean selected temperature between day and night, 3) has the same metabolic rate during the day and night, 4) selects termites over other prey types, 5) can detect prey using only auditory or olfactory senses, and 6) experiences lower predation risk at night than during the day. C.pantherinus shows many features of diurnal skink species, with a high mean selected temperature (36.1+/-1.6 degrees C) that is the same night and day, and a 32% lower metabolic rate at night than during the day. C.pantherinus selects termite prey over other insects and can detect prey using only auditory and olfactory senses; models of C. pantherinus experienced less predation at night than during the day. Preference for termites and reduced predation risk at night favour opportunistic nocturnal activity in this predominantly diurnal lizard and may contribute to its wide geographic distribution in arid Australia.

Response to Allen ‘An alternative hypothesis to the conclusion of Colman et al. (2014)’

We respond to the criticisms of Allen [[1][1]] regarding Colman et al . [[2][2]], examining the differences in forest mammal assemblages between areas where dingoes were controlled and not controlled in southeastern Australia. Allen [[1][1]] contends that: (i) Colman et al . [[2][2]] did not show

Divergent foraging behaviour of a desert rodent, Notomys fuscus, in covered and open microhabitats revealed using giving up densities and video analysis

We used a combination of giving up densities (GUD) and behavioural analysis from video footage to test the response of an Australian desert rodent, Notomys fuscus, to the experimental provision of cover microhabitat in the Strzelecki Desert, Australia. In many ecosystems, cover microhabitats are considered to be safe foraging locations for rodents. The response of bipedal desert rodents to cover microhabitats is less certain, with varied findings, due to their use of open habitats for fast travel. Notomys fuscus returned lower GUDs in cover than in open microhabitats and moved slowly for a greater amount of time under cover than in the open. These results suggest that N. fuscus has a preference for foraging under cover, where predation risk is lower, and under these conditions took longer to assess the cover microhabitat before foraging. This was distinctly different to the ‘get in, get out’ behaviour associated with foraging in open habitats. We advocate for the combined measurement of GUD and behavioural analysis using video footage as a way to improve understanding of rodents’ foraging behaviour.