BREEDING AND WEANING
An egg is laid 16-24 d after mating, hatches after a 10-11 d incubation, the PY is carried for 23-63 d before being deposited in a burrow where the burrow young (BY) is nursed every 3-6 d before weaning at 130-214 d (Ferguson and Laming 2022).
Advances in husbandry and management of echidnas has resulted in successful breeding at several Australian zoos (Ferguson and Turner 2013; Wallage et al. 2015; Ferguson and Laming 2022; Taronga Zoo records). Both free-ranging (Morrow et al. 2009) and zoo echidnas have produced young in consecutive years, are seasonally polyoestrus (Johnston and Keeley 2015; Dutton- Regester et al. 2021) and likely induced ovulators (Nicol et al. 2019a; Nicol et al. 2019b). A first-generation female laid an egg at 2 yr of age, giving the earliest estimation of puberty in the echidna (Taronga Zoo records). Sexual maturity was previously observed at 3 yr in zoo-housed (Wallage et al. 2015) and from 5-12 yr in free-ranging echidnas (Rismiller and McKelvey 2003). Wallage et al. (2015) debunked the theory that echidna trains (a characteristic displayed by echidnas during the breeding season where males line up one behind the other following a female) are necessary for breeding success, with successful breeding resulting from pairing the same echidnas in consecutive years. In zoos, the same male and female pairing may breed in successive years, despite the presence of other reproductively viable echidnas, and it is thought that male and female compatibility is crucial for breeding. One theory is that the female determines her mate and that the purpose of the echidna train is for the female to select her desired male by waiting until he is directly behind her and then allowing him to mate (B Finlayson pers. comm.). However, in Tas. free-ranging female echidnas are mated during torpor (Morrow and Nicol 2009). Behavioural cues are useful for monitoring breeding. Peak frequency then cessation of male reproductive behaviours (urogenital sniffing, rolling and copulation attempts) indicate copulation has occurred. Female receptivity is <24 h. Increased pacing, reduced feeding time and intake indicates impending oviposition (Dutton-Regester et al. 2022). Other factors considered key to successful managed care breeding include provision of basking lamps, a suitable nursery box with temperatures not exceeding 25°C, a separate shelter box for the dam, ideal female body condition and removal of the male within 10 d of mating. To prevent disturbance to breeding echidnas, cameras are used to identify maternal behaviours associated with oviposition, incubation and hatching, and to visualise developing PY. Pouch checks should not occur before three weeks (Dutton-Regester et al. 2022; Ferguson and Laming 2022). Once the PY are deposited in the burrow, daily weights allow monitoring of nursing frequency and volume (Wallage et al. 2015; Ferguson and Laming 2022). Twins have been reported on three occasions, two of which were in zoos (Pierce et al. 2006; Johnston and Keeley 2015).In a Tasmanian population, only 20-25% of young survived to weaning and 60% died before hatching or within the first 2 wk of lactation. This is in part caused by disturbance of females in the nursery burrow by males (Nicol and Morrow 2012; Harris and Nicol 2014).
Weaning cues vary depending on the geographical range and subspecies of echidna. Weaning in free-ranging echidnas is more gradual than first thought, as evidenced by juveniles showing exploratory foraging behaviour and then returning to the nursery burrow. Juvenile Tasmanian echidnas leave the nursery burrow at 125-145 d and >1 kg bodyweight, returning at night. They abandon the burrow ~12 ± 6 d later. The dam only ceases returning to the burrow once it has been abandoned by the juvenile. Subsequently there is no further association and the young echidna is considered weaned (Morrow and Nicol 2012).
This pattern is observed in echidnas bred at Perth and Taronga Zoos with nursing continuing after self-emergence, sometimes up to 34-39 d (Ferguson and Laming 2022). This contrasts with prior reports of abrupt weaning once the dam ceases to return to the burrow after leaving the entrance open (Rismiller and McKelvey 2003; Augee et al. 2006). Interestingly, maternal suckling of young outside a nursery burrow has been observed 60 d after twins abandoned their burrow (Pierce et al. 2006).Time of weaning is related to bodyweight rather than age. Although there are significant differences in weaning age noted between free-ranging echidna sub-species, there is relative consistency in weaning weights (Morrow et al. 2009; Morrow and Nicol 2012). Tasmanian echidnas wean at around 147 d (range, 130-163) at ~1.5 kg. Kangaroo Is. echidnas wean at a slightly lower mean of 1.4 kg but are much older at 204-210 d (Rismiller and McKelvey 2003). One WA echidna weaned at 1.7 kg between 195 and 200 d (Abensperg-Traun 1989) and one Qld echidna weaned at around 165 d (Beard and Grigg 2000).
Zoo-bred echidnas first emergence occurs around 152-169 d and 1.4-1.6 kg (R Russell-Cook pers. comm.; Ferguson and Laming 2022).
Post pouch life, echidna young can be described as pre-emergent juveniles, burrow young or ‘puggles’ (<0.9 kg), post-emergent juveniles (0.9-1.6 kg) and (weaned) sub-adults (>1.6 kg). Sexual maturity may also be dependent upon echidnas reaching their long-term adult mass (Nicol et al. 2019a).
4.