Comparison of sympatric freshwater turtle populations from an urbanized Sydney catchment

Abstract

ABSTRACT1. Australian freshwater turtles are widely distributed throughout the continent, and in each river catchment there are at least two taxa. In south-eastern Australia Chelodina longicollis and forms of Emydura macquarii cohabit within a waterway, although they have been shown to partition habitat within the water column in nonurban bodies of water. Limited comparative data are available for the urban populations.2. Within urban Sydney C. longicollis (eastern long-necked turtle) and Emydura macquarii dharuk (Sydney short-necked turtle) share habitat. However, in contrast with non-urban studies of C. longicollis and other sympatric E. macquarii taxa, it was observed that the population profile of the two species was similar at all sites, and that C. longicollis were present in greater numbers than E. m. dharuk.3. The continued degradation of preferred habitat, low recruitment, and potential competition from introduced turtles place both species in a precarious position.4. The shallow, impounded waterways of the regulated urban bodies of water align more closely with the preferred habitat of C. longicollis than with that of forms of E. macquarii, which prefer deeper flowing waters or large wetlands adjacent to rivers. Emydura m. dharuk may be at greatest risk of extinction in urban areas.5. Across urban Sydney, the low numbers of E. m. dharuk compared with C. longicollis may be due to the lack of mobility of E. m. dharuk such that individuals tend to be stranded in sub-optimal habitat. In contrast, C. longicollis has a greater propensity for overland movement, and a preference for the 'new habitat' resulting from urban impacts on the associated waterways, and thus appears to be able to utilize these modified urban waters more successfully.

Suburbs: dangers or drought refugia for freshwater turtle populations?

“…Turtles as a group may respond in a number of ways to urbanization. Some species can persist or even thrive in modified habitats such as gardens, stormwater drainage lagoons, golf course ponds, and other urban water bodies (Conner et al 2005, Burgin and Ryan 2008, Plummer et al 2008, Ryan et al 2008, Eskew et al 2010). In some respects these disturbed habitats can be of high quality, as turtles using these habitats may be able to grow faster, mature at an earlier age, and have higher fecundity than those inhabiting less developed areas (Lindemann 1996, Budischak et al 2006).…”

Historical museum collections and contemporary population studies implicate roads and introduced predatory bullfrogs in the decline of western pond turtles

“…Full-size  DOI: 10.7717/peerj.9248/ fig-8 Nicholson et al (2020), PeerJ, DOI 10.7717/peerj.9248 14/23 (Burgin & Ryan, 2008;Howey & Dinkelacker, 2013). Such populations may persist for years, but they do so as part of the "living dead" (Lovich et al, 2018) that often characterize declining, long-lived species.…”

Peer Review #2 of "Historical museum collections and contemporary population studies implicate roads and introduced predatory bullfrogs in the decline of western pond turtles (v0.1)"

“…Multiple studies have observed or proposed that male-biased populations result in population declines or extirpations of freshwater turtles (Ceballos et al, 2016;Vanek & Glowacki, 2019), and a long-term study of two wood turtle (Glyptemys insculpta) populations in Connecticut, USA documented sharp declines coinciding with human-mediated reductions in adult females (Garber & Burger, 1995). Reduced juvenile production, the ultimate result of increased female mortality, has also been found to result in freshwater turtle population declines or extirpations (Burgin and Ryan, 2008;Howey & Dinkelacker, 2013). Such populations may persist for years, but they do so as part of the "living dead" (Lovich et al, 2018) that often characterize declining, long-lived species.…”