Spatial ecology of a ubiquitous Australian anteater, the short-beaked echidna (Tachyglossus aculeatus)

Habitat use over winter by short-beaked echidnas (Tachyglossus aculeatus) at an intermittently flowing creek in arid north-western New South Wales

The heterogeneity of resource distribution in arid environments plays an important role in habitat selection by consumers. The productivity of the riparian zones of intermittently flowing creeks is typically prolonged, relative to the hinterland, as moisture and nutrients concentrate there. Short-beaked echidnas, Tachyglossus aculeatus, sustain arid populations, attributed to ant and termite availability, low predation, and an ability to exploit habitat remnants. However, the scale of their movements in arid habitats is poorly understood. Thus, we investigated echidna home ranges and the importance of food and shelter availability in habitat selection over one winter. We focussed on the riparian zone of a creek at Mount Wood in Sturt National Park, north-western New South Wales, Australia. Radio tracking (VHF and GPS), scat and habitat selection analyses were conducted. Mean core and peripheral home range areas were 0.16 and 1.042 km2, respectively, with a mean home range overlap of 0.56 km2. Habitat selection differed between juveniles and adults and may have been driven by prey availability (predominantly ants). The preferred shelter was thick leaf litter. We concluded that habitat selection patterns were driven by prey availability (ants) and shelter (leaf litter).

Short-beaked echidna (Tachyglossus aculeatus) home range at Fowlers Gap Arid Zone Research Station, NSW

Echidnas (Tachyglossus aculeatus) are found Australia-wide and appear to be remarkably well-adapted to the arid zone, yet nearly all echidna research has been conducted in temperate, tropical and alpine zones. This study investigated the home range and movement of echidnas in western New South Wales. Radio telemetry tracking was used to locate the echidnas daily during the study period (March-May 2018, November 2018, March-May 2019 and August 2019); the observed home range was 1.47± 1.21km2. This is over twice the reported home range of temperate environments (<0.65km2), suggesting that echidnas exhibit larger home ranges in arid zones. The home range of individual echidnas ranged from 0.02km2 to 3.56km2. Echidnas exhibited a small degree of overlap (6.6%± 19.8%) but this varied considerably between individuals (between 0 to 84.2% overlap.) Four out of the thirteen echidnas died during this study, likely due to the severe drought that occurred during the study. This study provides insight into the movement and home range of echidnas in arid zones, revealing that desert echidnas have large home ranges, probably dependent on the availability of resources.

Tachyglossus aculeatus (Monotremata: Tachyglossidae)

Tachyglossus aculeatus (Shaw, 1792) is a monotreme commonly called the short-beaked echidna. Although considered Australia’s most common native mammal because of its continent-wide distribution, its population numbers everywhere are low. It is easily distinguished from all other native Australian mammals because of its spine-covered body, hairless beak, and unique “rolling” gait. The five subspecies, one of which is found in Papua New Guinea, show variations in fur density, spine diameter, length, and number of grooming claws. The Kangaroo Island short-beaked echidna Tachyglossus aculeatus multiaculeatus is listed as “Endangered” but all other Tachyglossus are listed as “Least Concern” in the 2016 International Union for Conservation of Nature and Natural Resources Red List.

Energy Homeostasis in Monotremes

In 1803, the French anatomist Étienne Geoffroy Saint-Hilaire decided that the newly described echidna and platypus should be placed in a separate order, the monotremes, intermediate between reptiles and mammals. The first physiological observations showed monotremes had low body temperatures and metabolic rates, and the consensus was that they were at a stage of physiological development intermediate between "higher mammals" and "lower vertebrates." Subsequent studies demonstrated that platypuses and echidnas are capable of close thermoregulation in the cold although less so under hot conditions. Because the short-beaked echidna Tachyglossus aculeatus, may show very large daily variations in body temperature, as well as seasonal hibernation, it has been suggested that it may provide a useful model of protoendotherm physiology. Such analysis is complicated by the very significant differences in thermal relations between echidnas from different climates. In all areas female echidnas regulate Tb within 1°C during egg incubation. The lactation period is considered to be the most energetically expensive time for most female mammals but lactating echidnas showed no measurable difference in field metabolic rate from non-lactating females, while the lactation period is more than 200 days for Kangaroo Island echidnas but only 150 days in Tasmania. In areas with mild winters echidnas show reduced activity and shallow torpor in autumn and early winter, but in areas with cold winters echidnas enter true hibernation with Tb falling as low as 4.5°C. Monotremes do not possess brown adipose tissue and maximum rates of rewarming from hibernation in echidnas were only half those of marmots of the same mass. Although echidnas show very large seasonal variations in fat stores associated with hibernation there is no relationship between plasma leptin and adiposity. Leptin levels are lowest during post-reproductive fattening, supporting suggestions that in evolutionary terms the anorectic effects of leptin preceded the adiposity signal. BMR of platypuses is twice that of echidnas although maximum metabolism is similar. High levels of thyroid hormones in platypuses may be driving metabolism limited by low body temperature. Monotremes show a mosaic of plesiomorphic and derived features but can still inform our understanding of the evolution of endothermy.

A review of home-range studies on Australian terrestrial vertebrates: adequacy of studies, testing of hypotheses, and relevance to conservation and international studies

Describing the spatial requirements of animals is central to understanding their ecology and conservation needs. I reviewed 115 studies describing the home ranges of Australian terrestrial vertebrates that were published during 2001–12. Understanding the features that characterise best practice can guide future studies. I aimed to: evaluate the adequacy of these studies, examine the use of current analysis techniques, examine the application of home-range knowledge to species’ management, and examine hypotheses that seek to explain the size and location of home ranges. The reviewed studies were unevenly distributed across taxa with a majority (68%) involving mammals compared with birds (12%), reptiles (19%) and frogs (1%). Many studies had various shortcomings, suggesting that they had not fully described home ranges; many (41%) involved 10 or fewer individuals, ≤50 locations per individual (44%), and spanned periods of ≤3 months (46%). Studies of short duration risk underestimating home-range area and overlooking seasonal habitat use. Global positioning system telemetry was used in 10% of Australian studies. Many were also of short duration. Despite frequent criticism in the literature, the Minimum Convex Polygon was the most frequently used home-range estimator (84% of studies), followed by the Fixed Kernel (45% of studies). Applying knowledge of home ranges appears to be underappreciated, with only 39% of studies explicitly aiming to address management or conservation issues. Only three studies tested hypotheses that may explain home-range characteristics. Resource (food and shelter) distribution and, in one case, its heterogeneity, shaped home-range characteristics. I found that most studies use the term ‘home range’ in an indiscriminate way. Only 11% of studies within the international literature used qualifying terms (e.g. seasonal, annual). Tracking period is shown to influence home-range estimates. Therefore, I recommend that qualifying terms be used more frequently to avoid confusion when referring to animal home ranges.

A one night stand? Reproductive excursions of female roe deer as a breeding dispersal tactic

Breeding dispersal, defined as the net movement between successive breeding sites, remains a poorly understood and seldom reported phenomenon in mammals, despite its importance for population dynamics and genetics. In large herbivores, females may be more mobile during the breeding season, undertaking short-term trips (excursions) outside their normal home range. If fertilisation occurs, leading to gene flow of the male genome, this behaviour could be considered a form of breeding dispersal from a genetic point of view. Here, we investigated ranging behaviour of 235 adult roe deer using intensive GPS monitoring in six populations across Europe within the EURODEER initiative. We show that excursions are common from June to August among females, with 41.8% (vs. 18.1% of males) making at least one excursion. Most individuals performed only one excursion per season and departure dates for females were concentrated in time, centred on the rutting period, suggesting a link with reproduction. The distance females travelled during excursions was significantly greater than the site-specific average diameter of a male home range, while travel speed decreased once they progressed beyond this diameter, indicating search behaviour or interaction with other male(s) outside the resident male's territory. Because adults are normally highly sedentary, the potential for mating with relatives is substantial; hence, we conclude that rut excursions could be an alternative tactic enabling females to avoid mating with a closely related male. To understand better the ultimate drivers at play, it will be crucial to explore the genetic causes and consequences of this behaviour.

Brain and behaviour of living and extinct echidnas

The Tachyglossidae (long- and short-beaked echidnas) are a family of monotremes, confined to Australia and New Guinea, that exhibit striking trigeminal, olfactory and cortical specialisations. Several species of long-beaked echidna (Zaglossus robusta, Zaglossus hacketti, Megalibgwilia ramsayi) were part of the large-bodied (10 kg or more) fauna of Pleistocene Australasia, but only the diminutive (2-7 kg) Tachyglossus aculeatus is widespread today on the Australian mainland. We used high-resolution CT scanning and other osteological techniques to determine whether the remarkable neurological specialisations of modern echidnas were also present in Pleistocene forms or have undergone modification as the Australian climate changed in the transition from the Pleistocene to the Holocene. All the living and extinct echidnas studied have a similar pattern of cortical gyrification that suggests comparable functional topography to the modern short-beaked form. Osteological features related to olfactory, trigeminal, auditory and vestibular specialisation (e.g., foramina and cribriform plate area, osseous labyrinth topography) are also similar in living and extinct species. Our findings indicate that despite differences in diet, habitat and body size, the suite of neurological specialisations in the Tachyglossidae has been remarkably constant: encephalisation, sensory anatomy and specialisation (olfactory, trigeminal, auditory and vestibular), hypoglossal nerve size and cortical topography have all been stable neurological features of the group for at least 300,000 years.

Observations of breeding behaviour and possible infanticide in a wild population of Tasmanian echidnas (Tachyglossus aculeatus setosus)

We describe field observations of Tasmanian echidna behaviour, including possible infanticide, where males damaged and entered nursery burrows. We also present the second report of a female producing a second offspring within a single reproductive season after the loss of her first young at an early stage.

Identification of desmostanol as a novel vertebrate sterol in short-beaked echidna secretions

Mass spectra and chromatographic data are presented to support the identification of cholest-24-en-3β-ol (desmostanol) in odorous secretions in Tasmanian short-beaked echidnas. This sterol has previously been described only in marine invertebrates and phytoplankton, and may have a role in chemical communication in the echidna.

Movements and cumulative range size of the platypus (Ornithorhynchus anatinus) inferred from mark–recapture studies

The extent of mammalian movements often varies with size, sex and/or reproductive status. Fyke nets were set along streams and rivers near Melbourne (southern Victoria) from the mid-1990s to 2007, and in the Wimmera River catchment (western Victoria) from 1997 to 2005, to assess how far platypus of different age and sex classes travelled between captures and over longer periods. The mean distance between consecutive captures of adults did not vary significantly as intervals increased from 1–3 months to >3 years, suggesting that most individuals occupied stable ranges. However, adult females travelled, on average, only 35% as far between captures as males in southern Victoria, and 29% as far in the Wimmera. Up to half of this difference may be explained by variation in size-related metabolic requirements. Immature males and females respectively moved 61% and 53% as far, on average, as their adult equivalents, although two young males dispersed >40 km. Adults incrementally occupied up to 13.9 km of channel in the case of a male (based on six captures over 67 months) and 4.4 km of channel in the case of a female (based on five captures over 127 months).

Influence of habitat on home-range size in the short-beaked echidna

The size of an animal’s home range is strongly influenced by the resources available within it. In productive, resource-rich habitats sufficient resources are obtainable within a smaller area, and for many species, home ranges are smaller in resource-rich habitats than in habitats with lower resource abundance. Location data on 14 male and 27 female echidnas (Tachyglossus aculeatus) fitted with tracking transmitters, in the southern midlands of Tasmania, were used to test the influence of habitat type on home-range size. We hypothesised that as woodland should offer more shelter, food resources and refuges than pasture, echidnas living in woodland would have smaller home ranges than those living in pasture areas. We found significant differences between the sexes. Male echidnas had a significantly larger mean home range than females and a quite different relationship between home-range size and habitat type from females. There was no relationship between the proportion of woodland within male home ranges and home-range size whereas female echidnas had a highly significant negative relationship. This suggests that home-range size of female echidnas is highly influenced by the amount of woodland within it, but the home-range size of male echidnas is controlled by factors other than habitat. This pattern is consistent with the spatial ecology of many other solitary species with a promiscuous mating system. The home ranges of females are scaled to encompass all necessary resources for successfully raising their young within a minimal area, whilst the large home ranges of males are scaled to maximise access to females.