Moving house: long-term dynamics of corticosterone secretion are unaltered in translocated populations of a rare reptile (the tuatara, Sphenodon punctatus)

Abstract

Translocations are an important conservation tool used to restore at-risk species to their historical range. Unavoidable procedures during translocations, such as habitat disturbance, capture, handling, processing, captivity, transport and release to a novel environment, have the potential to be stressful for most species. In this study, we examined acute and chronic stress (through the measurement of the glucocorticoid corticosterone) in a rare reptile (the tuatara, Sphenodon punctatus). We found that: (i) the acute corticosterone response remains elevated during the initial translocation process but is not amplified by cumulative stressors; and (ii) the long-term dynamics of corticosterone secretion are similar in translocated and source populations. Taken together, our results show that translocated tuatara are generally resistant to cumulative acute stressors and show no hormonal sign of chronic stress. Translocation efforts in tuatara afford the potential to reduce extinction risk and restore natural ecosystems.

Keywords: Corticosterone; reptile; stress; translocation; tuatara.

Figure 1:

Populations involved in short- and long-term monitoring of physiological data (corticosterone) throughout a conservation translocation programme in New Zealand. Source populations (open circles) and translocated populations (filled circles) are shown.

Figure 2:

Schematic diagram of short-term (upper panel) and long-term monitoring (lower panel) during the translocations to Motuihe Island from Lady Alice Island in March 2012 (translocation ‘A’) and to Cape Kidnappers and Sanctuary Mountain Maungatautari from Stephens Island in October 2012 (translocation ‘B’). Short-term monitoring was carried out during translocation A only. Comparisons for long-term monitoring were made between source (dark grey) and translocated populations (light grey). The sex ratio (M:F) for each population is shown.

Figure 3:

Short-term monitoring. The corticosterone response (in nanograms per millilitre) of tuatara (Sphenodon punctatus) at different stages of the translocation process during translocation A to Motuihe Island from Lady Alice Island in March 2012. Sample size (n) is indicated by the number at the base of each bar. Bars that share identical letters are not significantly different (P > 0.05).

Figure 4:

Long-term monitoring. Dynamics of corticosterone (CORT) secretion (shown as means + SEM) in populations of tuatara (S. punctatus) translocated to: (a) Motuihe Island from Lady Alice Island (LA); and (b) Cape Kidnappers Sanctuary (CK) and Sanctuary Mountain Maungatautari (MT) from Stephens Island (ST). Sample size (n) is indicated by the number at the base of each bar and represents a paired sampled of baseline CORT (black bars) and the CORT response (3 h minus 0 h; grey bars) taken from all individuals. Bars that share identical letters are not significantly different (P > 0.05).

Figure 5:

Body condition scores (log mass/log snout–vent length) in populations of tuatara (S. punctatus) translocated to: (a) Motuihe Island from Lady Alice Island (LA); and (b) Cape Kidnappers Sanctuary (CK) and Sanctuary Mountain Maungatautari (MT) from Stephens Island (ST). Data points (means ± SEM) that share identical letters are not significantly different (P > 0.05).