Tachyglossus aculeatus
short-beaked echidna

Tachyglossus aculeatus is the most widely distributed extant monotreme. Subspecies of T. aculeatus are distributed throughout southern and eastern New Guinea, mainland Australia, Kangaroo Island, and Tasmania. This range includes large portions of the three countries of Australia, Indonesia, and Papua New Guinea. ("Tachyglossus aculeatus", 1991; Aplin et al., 2008; Groves, 2005)

Short-beaked echidnas thrive in a variety of habitats including open woodlands, savanna, agricultural areas, semi-arid, and arid regions. Both coastal and highland areas in New Guinea are home to Tachyglossus aculeatus, along with a range of ecosystems in Australia from mild coastal regions to above snowline. Short-beaked echidnas have a broad altitudinal range from sea level to at least 1,675 meters. (Aplin et al., 2008; Nicol and Anderson, 2007b)

Short-beaked echidnas are medium-sized mammals ranging in length from about 30 to 40 cm and in weight from about 2 to 7 kg. Depending on the subspecies and location, males or females may be larger. Short-beaked echidna spines are one of their most distinguishing characteristics. These spines cover the entire dorsal surface, including a small tail. Fur is also present and may be even longer than the spines in some subspecies. Tachyglossus aculeatus lacks external pinnae and teeth but does have hard pads in the back of the mouth. Short-beaked echidnas possess several adaptations to their foraging habits including tubular snouts, long sticky tongues, and front paws for digging. Males have non-venomous spurs on the ankles of their hind legs and females have pouches on their undersides. Both males and females have a cloaca through which feces, urine, and, in females, eggs pass. Males have penises they extend through the cloaca during mating. Short-beaked echidnas, and other monotremes, have low metabolic rates and low body temperatures, which may be related to such factors as diet and environmental variation. Short-beaked echidnas have larger brains than would be expected for their body mass. The cerebral cortex, in particular, is large and highly convoluted. (Nicol and Anderson, 2007b; Riek, 2008)

The longest recorded lifespan for Tachyglossus aculeatus is 50 years in captivity. There are anecdotal accounts of wild individuals living as long as 45 years. There is no doubt this species is particularly long-lived, especially for its size. A lifespan of 50 years is 3.7 times longer than would be expected based on echidna body size. Other long-lived mammals have been observed to have peroxidation-resistant membrane composition, which describes the ratio between polyunsaturates and monounsaturates in membrane lipids. Short-beaked echidna membranes were found to have lower polyunsaturate and higher monounsaturate levels than expected. This composition indicates peroxiclation-resistant cellular membranes in T. aculeatus. Lifespan is also associated with the production of free radicals, which is proportional to metabolic rate. Short-beaked echidnas have notably low metabolic rates, with the exception of times of arousal from torpor. During these arousal periods, metabolic rates increase by up to nine times that of basal metabolic rates and free radical production is high. Therefore, T. aculeatus is thought to have stress resistance that contributes to a long lifespan. A large and complexly-structured brain may be involved with longevity in T. aculeatus. Such brain characteristics are often correlated with life history traits like slow maturation and single births in other mammals. These traits, in turn, correlate with a long lifespan. (Hulbert, Beard, and Grigg, 2008; Nicol and Anderson, 2007b)

Short-beaked echidnas are semi-fossorial, digging in substrate for hibernation cover and to construct nursery burrows. They decrease energy usage by hibernating from early autumn to late spring. Short-beaked echidnas reduce their body temperature to 8 to 10 degrees C during torpor and use behavioral thermoregulation to maintain that preferred body temperature. During early hibernation, individuals prefer cooler soil temperatures compared with the coldest period of hibernation, at which time they will move to warmer hibernacula. During hibernation there are periodic arousals from torpor. The timing of hibernation seasons varies by subspecies, geographic location, sex, and reproductive state. Short-beaked echidnas are flexible in their exploitation of substrates for hibernacula, commonly using leaf litter and grass tussocks. (Nicol and Anderson, 2007a; Nicol and Anderson, 2007b)

Home Range

Short-beaked echidnas nest at temporary sites, and have overlapping home ranges. Their movements depend on food availability and not territoriality. ("Tachyglossus aculeatus", 1991; Nicol and Anderson, 2007b)

Short-beaked echidnas sense other echidnas predominantly through smell. Recent findings suggest feces piles act as an important intra-specific form of communication. (Elridge and Mensing, 2007; Nicol and Anderson, 2007b)

Adult short-beaked echidnas eat ants, termites, and other invertebrates. They make foraging pits by disturbing the soil when looking for food, and they prefer foraging under the canopies of large trees. Their long snouts and sticky tongues reflect their specialized diet. Short-beaked echidnas dig into ant and termite nests with their front paws and poke their long, sticky tongue into nest crevices and grinds insects with its tooth pads. Their foraging habits make separating soil from food difficult. Thus, much of their feces consists of soil. (Elridge and Mensing, 2007; Nicol and Anderson, 2007b)

Predation is not a major threat to short-beaked echidnas, even though feral cats, pigs, dingoes, and goannas are occasional predators. Animal predators are mostly a threat to young in burrows and to subadults. Adults escape predation by hiding beneath rocks or logs, or digging into the ground until only the spiny back is exposed. Short-beaked echidnas can also curl up to protect their undersides. Despite the minimal defense of many hibernaculum materials, predation on hibernating individuals does not seem to be a problem. After introduced predators, the biggest influence on T. aculeatus mortality is the threat of motor vehicles. Over-hunting by humans may become a problem in some areas of New Guinea. (Aplin et al., 2008; Nicol and Anderson, 2007b)

The foraging pits short-beaked echidnas create become resource traps and affect soil biogeochemistry. Tachyglossus aculeatus may be important in maintaining proper nutrient circulation through small-scale patchiness in semi-arid regions. (Elridge and Mensing, 2007)

Because short-beaked echidnas can live in agricultural areas, they may disrupt fields and gardens while foraging. (Nicol and Anderson, 2007b)

Short-beaked echidnas are hunted for food and for ceremonial purposes, especially in New Guinea. They maintain small-scale patchiness, which is an important ecosystem service that keeps semi-arid regions functioning properly. Their diet of ants, termites, and other invertebrates may contribute to the control of these species. (Aplin et al., 2008; Elridge and Mensing, 2007; Nicol and Anderson, 2007b)

As of 2008, the IUCN listed Tachyglossus aculeatus as a species of Least Concern. Short-beaked echidnas have a broad distribution, a large total population with a stable trend, and are tolerant of many habitat types. They occur in protected areas and appear to lack major threats. The IUCN did suggest monitoring the number of T. aculeatus killed on major tourist roads. (Aplin et al., 2008)