Animal lifestyle affects acceptable mass limits for attached tags.

Animal-attached devices have transformed our understanding of vertebrate ecology. To minimize any associated harm, researchers have long advocated that tag masses should not exceed 3% of carrier body mass. However, this ignores tag forces resulting from animal movement. Using data from collar-attached accelerometers on 10 diverse free-ranging terrestrial species from koalas to cheetahs, we detail a tag-based acceleration method to clarify acceptable tag mass limits. We quantify animal athleticism in terms of fractions of animal movement time devoted to different collar-recorded accelerations and convert those accelerations to forces (acceleration × tag mass) to allow derivation of any defined force limits for specified fractions of any animal's active time. Specifying that tags should exert forces that are less than 3% of the gravitational force exerted on the animal's body for 95% of the time led to corrected tag masses that should constitute between 1.6% and 2.98% of carrier mass, depending on athleticism. Strikingly, in four carnivore species encompassing two orders of magnitude in mass (ca 2-200 kg), forces exerted by '3%' tags were equivalent to 4-19% of carrier body mass during moving, with a maximum of 54% in a hunting cheetah. This fundamentally changes how acceptable tag mass limits should be determined by ethics bodies, irrespective of the force and time limits specified.

Passive acoustic monitoring for detecting the Yellow-bellied Glider, a highly vocal arboreal marsupial.

Passive acoustic monitoring (PAM) is increasingly being used for the survey of vocalising wildlife species that are otherwise cryptic and difficult to survey. Our study aimed to develop PAM guidelines for detecting the Yellow-bellied Glider, a highly vocal arboreal marsupial that occurs in native Eucalyptus forests in eastern and south-eastern Australia. To achieve this, we considered the influence of background noise, weather conditions, lunar illumination, time since sunset and season on the probability of detecting vocalisations. We deployed Autonomous Recording Units (ARUs) at 43 sites in the Central Highlands of Victoria during two periods: spring/summer (October 2018 to January 2019), and autumn/winter (May to August 2019). ARUs were programmed to record for 11 hours from sunset for 14 consecutive days during each period. Background noise resulted from inclement weather (wind and rain) and masked vocalisations in spectrograms of the recordings, thus having the greatest influence on detection probability. Vocalisations were most common in the four hours after sunset. Rainfall negatively influenced detection probability, especially during the autumn/winter sampling period. Detection of Yellow-bellied Gliders with PAM requires deploying ARUs programmed to record for four hours after sunset, for a minimum of six nights with minimal inclement weather (light or no wind or rain). The survey period should be extended to 12 nights when rain or wind are forecast. Because PAM is less labour intensive than active surveys (i.e., spotlighting and call playbacks with multiple observers and several nights' survey per site), its use will facilitate broad-scale surveys for Yellow-bellied Gliders.

Passive acoustic surveys for predicting species' distributions: Optimising detection probability.

Surveying terrestrial species across diverse habitats is important for predicting species' distributions and implementing conservation actions. For vocalising species, passive acoustic monitoring (PAM) is increasing in popularity; however, survey design rarely considers the factors influencing the timing and occurrence of vocalisations and in turn, how they may influence detectability of the species. Here, we use the koala (Phascolarctos cinereus) as a case study to show how PAM can be used to first examine the factors influencing vocalisations, and then use occupancy modelling to make recommendations on survey design for the species. We used automated recording units to monitor koala vocalisations at ten sites between August 2016 and January 2017. The timing of male koala vocalisations was linked to time of sunset with vocalisations increasing two hours prior to sunset and peaking at four hours after sunset. Vocalisations had a seasonal trend, increasing from the early to middle stage of the breeding season. Koala population density and stage of the breeding season had more influence on detection probability than daily sampling schedule. Where population density was low, and during the early stage of the breeding season, 7 survey nights (recording for 6 hours from 20:00h to 02:00h; i.e. the period of peak bellowing activity) were required to be 95% confident of a site-specific absence. Our study provides an approach for designing effective passive acoustic surveys for terrestrial species.

Failure to Respond to Food Resource Decline Has Catastrophic Consequences for Koalas in a High-Density Population in Southern Australia.

Understanding the ability of koalas to respond to changes in their environment is critical for conservation of the species and their habitat. We monitored the behavioural response of koalas to declining food resources in manna gum (Eucalyptus viminalis) woodland at Cape Otway, Victoria, Australia, from September 2011 to November 2013. Over this period, koala population density increased from 10.1 to 18.4 koalas.ha-1. As a result of the high browsing pressure of this population, manna gum canopy condition declined with 71.4% manna gum being completely or highly defoliated in September 2013. Despite declining food resources, radio collared koalas (N = 30) exhibited high fidelity to small ranges (0.4-1.2 ha). When trees became severely defoliated in September 2013, koalas moved relatively short distances from their former ranges (mean predicted change in range centroid = 144 m) and remained in areas of 0.9 to 1.0 ha. This was despite the high connectivity of most manna gum woodland, and close proximity of the study site (< 3 km) to the contiguous mixed forest of the Great Otway National Park. Limited movement had catastrophic consequences for koalas with 71% (15/21) of radio collared koalas dying from starvation or being euthanased due to their poor condition between September and November 2013.

Activity patterns of free-ranging koalas (Phascolarctos cinereus) revealed by accelerometry.

An understanding of koala activity patterns is important for measuring the behavioral response of this species to environmental change, but to date has been limited by the logistical challenges of traditional field methodologies. We addressed this knowledge gap by using tri-axial accelerometer data loggers attached to VHF radio collars to examine activity patterns of adult male and female koalas in a high-density population at Cape Otway, Victoria, Australia. Data were obtained from 27 adult koalas over two 7-d periods during the breeding season: 12 in the early-breeding season in November 2010, and 15 in the late-breeding season in January 2011. Multiple 15 minute observation blocks on each animal were used for validation of activity patterns determined from the accelerometer data loggers. Accelerometry was effective in distinguishing between inactive (sleeping, resting) and active (grooming, feeding and moving) behaviors. Koalas were more active during the early-breeding season with a higher index of movement (overall dynamic body acceleration [ODBA]) for both males and females. Koalas showed a distinct temporal pattern of behavior, with most activity occurring from mid-afternoon to early morning. Accelerometry has potential for examining fine-scale behavior of a wide range of arboreal and terrestrial species.

Free-ranging male koalas use size-related variation in formant frequencies to assess rival males.

Although the use of formant frequencies in nonhuman animal vocal communication systems has received considerable recent interest, only a few studies have examined the importance of these acoustic cues to body size during intra-sexual competition between males. Here we used playback experiments to present free-ranging male koalas with re-synthesised bellow vocalisations in which the formants were shifted to simulate either a large or a small adult male. We found that male looking responses did not differ according to the size variant condition played back. In contrast, male koalas produced longer bellows and spent more time bellowing when they were presented with playbacks simulating larger rivals. In addition, males were significantly slower to respond to this class of playback stimuli than they were to bellows simulating small males. Our results indicate that male koalas invest more effort into their vocal responses when they are presented with bellows that have lower formants indicative of larger rivals, but also show that males are slower to engage in vocal exchanges with larger males that represent more dangerous rivals. By demonstrating that male koalas use formants to assess rivals during the breeding season we have provided evidence that male-male competition constitutes an important selection pressure for broadcasting and attending to size-related formant information in this species. Further empirical studies should investigate the extent to which the use of formants during intra-sexual competition is widespread throughout mammals.

Effect of diphacinone on blood coagulation in Spermophilus beecheyi as a basis for determining optimal timing of field bait applications.

The effect was determined of a single dose of 2 mg kg-1 diphacinone on three blood-clotting parameters [Prothrombin Time (PT), Partial Thromboplastin Time (PTT), and Protein Induced by Vitamin K Absence or Antagonists (PIVKA)] over a 120-h period in California ground squirrels, Spermophilus beecheyi. Diphacinone resulted in elevated PT, PTT and PIVKA within 24 h of squirrels receiving the dose. The most significant change was observed 72 h after dosing. As time following diphacinone dosing increased, there was higher individual variation in blood-clotting time. We suggest that increasing the interval between field bait applications should still result in squirrel mortality but reduce the potential for secondary hazards that may occur when squirrels have the opportunity to consume more than one lethal dose of diphacinone.