Abstract
Assemblages of introduced taxa provide an opportunity to understand how abiotic and biotic factors shape habitat use by coexisting species. We tested hypotheses about habitat selection by two deer species recently introduced to New Zealand’s temperate rainforests. We hypothesised that, due to different thermoregulatory abilities, rusa deer (Cervus timorensis; a tropical species) would prefer warmer locations in winter than red deer (Cervus elaphus scoticus; a temperate species). Since adult male rusa deer are aggressive in winter (the rut), we also hypothesised that rusa deer and red deer would not use the same winter locations. Finally, we hypothesised that in summer both species would prefer locations with fertile soils that supported more plant species preferred as food. We used a 250 × 250 m grid of 25 remote cameras to collect images in a 100-ha montane study area over two winters and summers. Plant composition, solar radiation, and soil fertility were also determined for each camera location. Multiseason occupancy models revealed that direct solar radiation was the best predictor of occupancy and detection probabilities for rusa deer in winter. Multistate, multiseason occupancy models provided strong evidence that the detection probability of adult male rusa deer was greater in winter and when other rusa deer were present at a location. Red deer mostly vacated the study area in winter. For the one season that had sufficient camera images of both species (summer 2011) to allow two-species occupancy models to be fitted, the detection probability of rusa deer also increased with solar radiation. Detection probability also varied with plant composition for both deer species. We conclude that habitat use by coexisting tropical and temperate deer species in New Zealand likely depends on the interplay between the thermoregulatory and behavioural traits of the deer and the abiotic and biotic features of the habitat.
Highlights
Understanding why animal species do or do not use a location has long been a fundamental question in ecology [1,2,3,4,5]
There were 115 rusa deer images in each of the four seasons studied, red deer were not recorded on any images in winter 2010, and they were recorded on only 2 images in winter 2011
Rusa deer images were recorded at 100% of the 25 camera locations at some point over the total period comprising the four seasons sampled, and red deer were recorded at 80% of the locations
Summary
Understanding why animal species do or do not use a location has long been a fundamental question in ecology [1,2,3,4,5]. Contemporary habitat use and activity reflects the current role of abiotic and biotic factors, and the influence of evolutionary history [5]. It can be difficult to distinguish whether contemporary habitat use and activity are the result of current factors or legacies of a coevolved history [5, 9]. An emerging opportunity for understanding how current abiotic and biotic factors alone shape the use of habitat by (and activity of) coexisting species is through studying recent assemblages of introduced species. In such ecosystems, behavioural and/or morphological features are expressed through contemporary habitat selection only in response to current abiotic and biotic factors
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