This is the first detailed ecological study of the Cape York antechinus, Antechinus leo, a small marsupial endemic to rainforest on the Cape York Peninsula, North Queensland, Australia. A total of 181 animals was captured 725 times at Iron Range during a capture–mark–recapture study from 1989 to 1991. A. leo is crepuscular–nocturnal, insectivorous, semi-arboreal and nests in hollows. Its life-history strategy is typical of the genus, including the synchrony of reproductive events and the post-mating death of all males. The estimated annual mating season is from mid-September to mid-October. Young were born around 1 November ( 12 days), and were carried in the pouch until early to mid December. Juveniles became trappable around mid February. Daughters stayed in their mother's home range, while sons dispersed soon after they left the nest. Lactation, weaning and dispersal of young were timed to coincide with the wet season when the abundance of invertebrates increased, suggesting that populations are limited by food supply.
Sodium cyanide poison is potentially a more humane method to control wild dogs than sodium fluoroacetate (1080) poison. This study quantified the clinical signs and duration of cyanide toxicosis delivered by the M-44 ejector. The device delivered a nominal 0.88 g of sodium cyanide, which caused the animal to loose the menace reflex in a mean of 43 s, and the animal was assumed to have undergone cerebral hypoxia after the last visible breath. The mean time to cerebral hypoxia was 156 s for a vertical pull and 434 s for a side pull. The difference was possibly because some cyanide may be lost in a side pull. There were three distinct phases of cyanide toxicosis: the initial phase was characterised by head shaking, panting and salivation; the immobilisation phase by incontinence, ataxia and loss of the righting reflex; and the cerebral hypoxia phase by a tetanic seizure. Clinical signs that were exhibited in more than one phase of cyanide toxicosis included retching, agonal breathing, vocalisation, vomiting, altered levels of ocular reflex, leg paddling, tonic muscular spasms, respiratory distress and muscle fasciculations of the muzzle.
Abstract ContextEcotones are recognised globally as areas of high biodiversity, yet relatively little is known about how fauna use different types of ecotone. Tropical rainforest–grassland ecotones are shaped through particular fire regimes, creating both gradual and abrupt ecotones. Insectivorous bats contribute considerably to mammalian diversity, and their capacity for flight allows them to use ecotones in a three-dimensional way, making them an informative faunal group for evaluating ecotone use. AimsTo critically evaluate how insectivorous bats use gradual and abrupt ecotones between rainforest and grassland habitats. MethodsBat detectors were placed every 50m, along 200-m transects, through five gradual and five abrupt rainforest–grassland ecotones. The activity of all insectivorous bats, as well as open, edge–open and closed foraging guilds (defined by echolocation call type), was compared among grassland and rainforest habitats, gradual and abrupt ecotones and positions across the ecotones. Key resultsMean total bat activity, mean open and edge–open foraging guild activity were significantly higher in grassland positions, followed by the edge, and were lowest in the rainforest. Closed foraging guild bats showed no preference for either habitats, but had significantly higher activity in gradual compared with abrupt ecotones. Mean activity of edge–open foraging guild bats was affected strongly by the interaction between ecotone type and position along the ecotone. Gradual ecotones had a more even proportion of all three bat foraging guilds along the ecotone compared with abrupt ecotones. Most of these findings were likely driven by the structural complexity of gradual ecotones that fulfilled microhabitat requirements for all three foraging guilds, but may also have been influenced by insect prey abundance. ConclusionsThe present study demonstrated the importance of grassland patches in a tropical, rainforest landscape, and of gradual rainforest–grassland ecotones for insectivorous bats. Gradual ecotones promote complex habitat mosaics to allow closed foraging guild species to take advantage of food resources provided by grasslands, and provide all bats proximity to potential roosting and foraging sites. ImplicationsThe data clearly suggest that a suitable fire regime should be used to maintain current grassland patches within a rainforest landscape, and to promote gradual ecotones for use by insectivorous bats.
Context Camera traps are available with infrared or white flash, with the former being more commonly used. However, white flash produces colour night-time photographs that can be critically useful for both species and individual identification. White flash was thought to cause more disturbance to wildlife than was infrared and this may lead to camera avoidance. Evaluating the extent of this response, and differences between the flash types, is useful to develop improved survey designs. Aims This research aimed to quantify the behavioural responses of Eld's deer to white and infrared flash, to determine whether white-flash cameras were suitable for use in population surveys of this species. Methods A behavioural ethogram was used to quantify the responses of the deer to the two flash types, as well as the responses of different sex-age classes and group sizes when encountering a camera trap. Additionally, the detection rate for white flash and infrared flash cameras was compared through time, to determine any pattern of avoidance. Key results While deer were more likely to observe and be startled by white flash than infrared, this did not adversely affect the detection of the deer, with no significant change in the detection rate between the two different flash types over time. Group size was found not to influence behavioural response when encountering camera traps, whereas different age–sex classes of deer showed very few differences in response to camera traps. Conclusions White flash cameras were found to be suitable for Eld's deer population surveys and were beneficial in providing colour night-time photos that allow for spotted female deer to be individually identified. Implications Practitioners should not be concerned about the influence of white flash when using camera traps to monitor populations of Eld's deer, and using white flash is recommended when individual identification is required.
Context Rice-field rodent pests cause substantial economic losses in Asia. In Vietnam, the rice-field rat (Rattus argentiventer) causes 5–10% annual pre-harvest loss in rice yield. A sound ecological knowledge of this species would be useful for developing strategies for managing this pest. Aims We tested the hypotheses that there would be changes in the population abundance, breeding performance and habitat use of R. argentiventer in response to rice-crop growth stage. Methods Capture–mark–recapture and kill trapping and spool-and-line tracking were used to assess population abundance, breeding and habitat use in different rice-bank habitats, at 3–5-week intervals, through a 2-month flooding period and a rice cropping season. The study was conducted between October 2008 and April 2009 in An Giang Province in The Mekong Delta, Vietnam. Key results The population abundance of R. argentiventer was significantly related to rice-crop growth stage and rice-bank habitat. More rats were captured after harvest (P < 0.001) and more were captured in the large and medium-sized banks (P < 0.05). The breeding performance of adult females responded to rice-crop growth stage (P = 0.006). When rice cover was sparse, adult females were located in the burrows during the day, whereas when the cover became abundant, adult females remained in the fields during both the day and at night time. After harvest, rats returned to utilise burrows along rice-field banks. Conclusions and implications (1) Rat control activities should be conducted prior to the seedling stage of the rice crop, before the onset of breeding and when vegetative cover is sparse, allowing the animals to be targeted in their burrows; and (2) vegetation on the rice-field banks should be cut to <10 cm to limit the availability of suitable nesting habitat in large and medium-sized banks.
Context The ricefield rat, Rattus argentiventer, is the main rodent pest of rice in Vietnam, causing annual pre-harvest rice losses of around 10%. Although its diet is reported to consist of mainly rice, other components might also be important, and it is not known whether its breeding performance is affected by the quality and/or quantity of food. Furthermore, if its breeding is synchronised with the growth of rice crops, the rats will be able to make full use of the food supply to produce offspring. This knowledge is necessary for developing improved strategies for managing this pest.
Aims This study aimed to determine whether the breeding performance of female R. argentiventer is responding to food quality (increased percentage of rice in stomach) and/or quantity (increased weight of stomach content) or whether its breeding is synchronised with the growth of rice crops.
Methods The stomach contents and breeding condition of 296 adult female rats were sampled by snap trapping once a month from October 2008 to December 2009 over three consecutive irrigated lowland rice crops fields to cover a range of rice growth stages in An Giang province, Mekong Delta, Vietnam.
Key results Overall, rice formed 70.5% ± 2.0 s.e. in the diet, followed by green material (25.9% ± 1.9 s.e.), insects (3.1% ± 0.6 s.e.) and mung bean (0.5% ± 0.3 s.e.). The probability of breeding increased with increasing mean percentage of rice in the diet: Pr(Breed) = 1/(1 + exp(0.6395–0.0090 × Rice)). However, this relationship was not consistent because breeding performance was high at the heading stage when the percentage of rice in the stomach was low and because breeding intensity was low at sowing when the percentage of rice in stomach was high. The rice growth stage is a better predictor for the breeding performance than the percentage of rice in the diet.
Conclusions Breeding was driven by a functional response of rats to the abundant supply of food quality (rice grain), modified by some unknown mechanisms that modifies this response of rats so that rats can anticipate food supply. Understanding the nature of this mechanism may provide insights into population processes that can be exploited in controlling rats in rice crops.
Implications Farmers could slow the reproductive rate of female R. argentiventer by reducing the food quantity through minimising the amount of spilt grain left in the field and through more synchronous cropping.
Context Free-roaming dogs are ubiquitous worldwide and pose a threat to wildlife. An understanding of the roaming behaviour of dogs is useful for developing effective management strategies. Aims We aimed to assess the activity ranges and patterns of free-roaming dogs in a rural Cambodian village. An adjacent wildlife sanctuary protects populations of threatened species that may be negatively impacted by dogs. Methods We used rudimentary hand-made GPS collars to track village dogs and quantify their movements. Activity ranges were calculated for male and female dogs, and the mean distances travelled at night and during the day were determined. Additionally, forays outside of the activity range were characterised. Key results We estimated a mean activity range of 178 ± 190 ha and found that dogs typically travelled longer distances at night. Females had significantly smaller activity ranges, as well as covering shorter distances per day. Foray behaviour was variable, with some dogs entering the wildlife sanctuary regularly and others not at all. Conclusions Free-roaming Cambodian dog activity overlapped with native mammals in the study site, posing a risk of predation, resource exclusion, harassment and competition of Cambodian species. Implications The data suggest that although dogs generally spend the majority of their time within the village, there is significant risk to wildlife. Actions are required to mitigate threats to native wildlife, in particular threatened species such as Eld's Deer.
Context The mitigation of feral pig (Sus scrofa) impacts in north Queensland's World Heritage tropical rainforests is constrained by the lack of an effective and target-specific poison baiting method. Aims This study aimed to determine whether easily implemented bait presentation methods or seasonal variation in bait acceptability could be used to selectively reduce the consumption of feral pig baits by non-target species. Methods We exposed manufactured feral pig baits to pigs and non-target species in the field, and compared bait encounter, sampling and consumption rates for different functional groups of species among three different types of bait presentation and composition. We then exposed baits under different seasonal conditions and related bait encounter and consumption by different functional groups to seasonally variable phenomena. Key results Shallow burial greatly reduced bait consumption by most non-target species, but not dingoes (Canis lupus dingo). Nocturnal bait distribution and seasonal baiting were less useful. Pigs showed substantial seasonal variation in physiological condition, suggesting that pigs should be more susceptible to consuming novel foods, such as baits, after periods of low rainfall. However, few pigs consumed the manufactured baits used in this study. Conclusions Manufactured baits are not currently suitable for widespread use in the region. However, shallow burial should provide an effective method of reducing non-target bait-take if baits can be made more attractive and acceptable to pigs and less acceptable to dingoes. Implications Future efforts to enable effective feral pig control in the region should focus on developing baiting materials that are more attractive to pigs and unappealing to dingoes.
Aims Sea-level rise is one of the most certain consequences of global warming and is predicted to exert significant adverse effects on wildlife in coastal habitats worldwide. Terrestrial fauna inhabiting low-lying islands are likely to suffer the greatest loss to habitat from sea-level rise and other oceanographic impacts stemming from anthropogenic climate change. Bramble Cay (Maizab Kaur), an ~4ha, low elevation sand cay located in Torres Strait, Australia, supports the only known population of the endangered Bramble Cay melomys Melomys rubicola Thomas, 1924. As a result of a decline in this population noted during previous monitoring to 2004, habitat loss due to erosion of the cay and direct mortality from storm surges were implicated as major threats to this species. This study aimed to confirm the current conservation status of the species, to seek information about the key factor or factors responsible for the population decline and to recover any remaining individuals for a captive insurance population. Methods During three survey periods (December 2011, March 2014 and August–September 2014), a total of 1170 small mammal trap-nights, 60 camera trap-nights, 5h of nocturnal searches and 5h of diurnal searches were undertaken on Bramble Cay. Key results All three survey periods failed to detect any Bramble Cay melomys. The island had experienced a recent, severe reduction in vegetation, which is the primary food resource for the Bramble Cay melomys. Herbaceous cover on the cay decreased from 2.16ha in 2004 to 0.065ha in March 2014 before recovering somewhat to 0.19ha in August–September 2014. Conclusions These results demonstrate that this rodent species has now been extirpated on Bramble Cay. The vegetation decline was probably due to ocean inundation resulting from an increased frequency and intensity of weather events producing extreme high water levels and storm surges, in turn caused by anthropogenic climate change. Implications The loss of the Bramble Cay melomys from Bramble Cay probably represents the first documented mammalian extinction due to human-induced climate change. This event highlights the immediate need to mitigate predicted impacts of sea-level rise and ocean inundation on other vulnerable species occurring on low lying islands and in susceptible coastal zones through captive breeding and reintroduction or other targeted measures.
The introgression of domestic dog genes into dingo populations threatens the genetic integrity of 'pure' dingoes. However, dingo conservation efforts are hampered by difficulties in distinguishing between dingoes and hybrids in the field. This study evaluates consistency in the status of hybridisation (i.e. dingo, hybrid or dog) assigned by genetic analyses, skull morphology and visual assessments. Of the 56 south-east Queensland animals sampled, 39 (69.6%) were assigned the same status by all three methods, 10 (17.9%) by genetic and skull methods, four (7.1%) by genetic and visual methods; and two (3.6%) by skull and visual methods. Pair-wise comparisons identified a significant relationship between genetic and skull methods, but not between either of these and visual methods. Results from surveying 13 experienced wild dog managers showed that hybrids were more easily identified by visual characters than were dingoes. A more reliable visual assessment can be developed through determining the relationship between (1) genetics and phenotype by sampling wild dog populations and (2) the expression of visual characteristics from different proportions and breeds of domestic dog genes by breeding trials. Culling obvious hybrids based on visual characteristics, such as sable and patchy coat colours, should slow the process of hybridisation.
