The private life of echidnas: using accelerometry and GPS to examine field biomechanics and assess the ecological impact of a widespread, semi-fossorial monotreme

Abstract

The short-beaked echidna (Tachyglossus aculeatus) is a monotreme and therefore provides a unique combination of phylogenetic history, morphological differentiation and ecological specialisation for a mammal. The echidna has a unique appendicular skeleton, a highly specialised myrmecophagous lifestyle and a mode of locomotion that is neither typically mammalian nor reptilian, but has aspects of both lineages. We therefore were interested in the interactions of locomotor biomechanics, ecology and movements for wild, free-living short-beaked echidnas. To assess locomotion in its complex natural environment, we attached both GPS and accelerometer loggers to the back of echidnas in both spring and summer. We found that the locomotor biomechanics of echidnas is unique, with lower stride length and stride frequency than reported for similar-sized mammals. Speed modulation is primarily accomplished through changes in stride frequency, with a mean of 1.39 Hz and a maximum of 2.31 Hz. Daily activity period was linked to ambient air temperature, which restricted daytime activity during the hotter summer months. Echidnas had longer activity periods and longer digging bouts in spring compared with summer. In summer, echidnas had higher walking speeds than in spring, perhaps because of the shorter time suitable for activity. Echidnas spent, on average, 12% of their time digging, which indicates their potential to excavate up to 204 m 3 of soil a year. This information highlights the important contribution towards ecosystem health, via bioturbation, of this widespread Australian monotreme.

Pectoral girdle and forelimb musculoskeletal function in the echidna (Tachyglossus aculeatus): insights into mammalian locomotor evolution

“…Monotremes are crucial in building a complete picture of mammalian forelimb evolution, but the clade is depauperate—represented by only three extant genera (the platypus, and short-beaked and long-beaked echidnas) and a poor fossil record [19]. Due to their relatively limited distribution and the endangered status of some species, monotremes have been subject to only a handful of locomotory studies [14,20–22], leaving many aspects of their functional anatomy unexplored. Here we build a musculoskeletal computer model of the pectoral girdle and forelimb in the short-beaked echidna Tachyglossus aculeatus to estimate maximal joint ranges of motion and muscle moment arms—fundamental descriptors of musculoskeletal geometry and function [23].…”

Quantifying koala locomotion strategies: implications for the evolution of arborealism in marsupials

“…The effect of body mass (kg) on stride length (m) and speed (m s −1 ) for the ground locomotion of six koalas compared with various mammals. Log:log relationship of (A) stride length (m), compiled from Reynolds (1987) ( primates: yellow), Strang and Steudel (1990) and Heglund and Taylor (1988), and (B) speed (m s −1 ) from Garland, 1983, Clemente et al (2016 The locomotion of the koala seems highly adapted for life in trees, which is not surprising given that they spend a significant amount of time locomoting in eucalypt canopies (Ryan et al, 2013). Their locomotory strategy likely results from their elongated limbs and strong grasping appendages shared with primates.…”

“…The locomotor performance of an individual limits its behaviour, and inherently fitness, within its niche (Irschick and Garland, 2001). The study of locomotor performance thus gives an understanding of both the challenges an animal may encounter within their environment, and the morphology that aids them in overcoming these (Byrnes and Spence, 2011;Clemente et al, 2016;Wynn et al, 2015). Arboreal habitats may represent one of the more challenging environments to animals, as they are typically characterised by compliant, discontinuous substrates, often at significant heights from the ground (Günther et al, 1991;Hyams et al, 2012;Youlatos et al, 2015), yet a range of phyla use trees for food and shelter (e.g.…”

Nighttime Ecology: The “Nocturnal Problem” Revisited

“…Seasonal switches may be quite common, with individuals typically being more diurnal when it is colder and more nocturnal when it is warmer (fig. 2 c & d, e & f; e.g., fish -Hautala 2008;mammals -Hayes and Krausman 1993;Maloney et al 2005;Bourgoin et al 2008;Zschille et al 2009;Erkert et al 2012;Hetem et al 2012;Giné et al 2015;Bu et al 2016;Clemente et al 2016;Hofmann et al 2016;Davimes et al 2017); the evolution of endothermy may have been associated with expanding daily activity into the night (Grigg et al 2004). The degree of nocturnal activity of a species can also be dependent on life stage, age and/or body size, sex, migratory phase, density, lunar phase, habitat, weather, and timing of prey activity (table 1, fig.…”