Comparative Biochemistry and Physiology Part A 135 (2003) 215–219 1095-6433/03/$ - see front matter  2003 Elsevier Science Inc. All rights reserved. PII: S1095-6433 Ž 03 . 00087-4 Energetic costs of tail loss in a montane scincid lizard Paul Doughty*, Richard Shine, Michael S.Y. Lee School of Biological Sciences, University of Sydney, Sydney, NSW 2006, Australia Received 7 November 2002; received in revised form 16 January 2003; accepted 16 January 2003 Abstract Most species of lizards will shed their tails at the point of contact when grasped by a predator. We investigated the energetic consequences of tail loss by measuring lipids in a scincid lizard that stores energy in its tail for reproduction. Most of the lipids were concentrated in the proximal portion of the tail. Thus, partial tail loss may not severely affect energy stores if the distal portion of the tail is shed in predatory encounters. We also found that the width of the tail was a reliable non-invasive index of energy reserves in this species.  2003 Elsevier Science Inc. All rights reserved. Keywords: Anti-predator defence; Caudal autotomy; Energetic index; Eulamprus tympanum; Lipids; Lizards 1. Introduction Lizards of many species autotomize their tails when seized by predators (Arnold, 1984, 1988; Bellairs et al., 1985). Tail autotomy usually facil- itates release from a predator but may entail longer- term costs (Wilson, 1992; Downes and Shine, 2000; but see Niewiarowski et al., 1997). In some species of lizards, the tail is an important storage organ for lipids (Bustard, 1967; Congdon et al., 1974; Daniels, 1984). Thus, loss of the tail may reduce energy stores and delay the animal’s next reproductive episode or reduce size and number of young (Smyth, 1974; Dial and Fitzpatrick, 1981; Wilson and Booth, 1998). We studied the lipid content in tails from south- ern water skinks, E. tympanum, a lizard species that lacks abdominal fat bodies (Greer, 1986). Hence, the tail constitutes the primary energy- *Corresponding author. Department of Zoology and Ento- mology, University of Queensland, Brisbane, QLD 4072, Australia. Tel.: q61-42-775-5360; fax: q61-7-3365-1655. E-mail address: p.doughty@mailbox.uq.edu.au (P. Doughty). storage system in this species. E. tympanum females rely on stored energy in the tail for reproduction (Doughty and Shine, 1997, 1998; Rohr, 1997), as do other related species (Smyth, 1974; Taylor, 1986; Wilson and Booth, 1998). Thus, we expect that tail autotomy would reduce energy stores for reproduction to a greater degree in this species than in most other lizards. By inducing autotomy in lizards and measuring the lipid content of removed tails, we (1) assessed whether simple measures of tailbase width offer valid non-invasive indices of energy storage (as used by Doughty and Shine, 1997, 1998); and (2) quantified the degree to which autotomy of differ- ent proportions of the entire tail reduces caudal energy stores. For example, if lipid stores are concentrated in the tailbase, loss of the distal half of the tail may result in only a small loss of stored energy. Southern water skinks are medium-sized (to 95 mm SVL, 130 mm tail length, 15 g) viviparous scincid lizards that are widely distributed through montane habitats in south-eastern Australia (Cog- ger, 1992). Fig. 1 depicts how the lipids are