Methods for Assessing Size at Birth and Postnatal Growth and Development in Bats

—0 —+1 SI Z E AT BI RT H A N D POST NATA L growth and development are important lifehistory traits (Case, 1978; Ricklefs, 1979; Ernest, 2003) because they refl ect major components of parental eff ort (Millar, 1977; Oftedal, 1984; Kirkwood, 1985; Costa et al., 1986; Gittleman and Oftedal, 1987; Oftedal and Gittleman, 1988; Harvey and Read, 1988; Read and Harvey, 1989; Promislow and Harvey, 1990; Ernest, 2003). Although analyses of these and other traits have become increasingly incorporated into lifehistory analyses of bats (Kurta and Kunz, 1987; Kunz and Stern, 1995; Hayssen and Kunz, 1996; Kunz and Hood, 2000; Barclay and Harder, 2003), they have seldom been included in lifehistory analyses of other mammals (e.g., Millar, 1981; Western and Ssemakula, 1982; Martin, 1984; Martin and McLarnon, 1985; Wootton, 1987; Harvey and Read, 1988; Read and Harvey, 1989; Promislow and Harvey, 1990; Sterns, 1992; Ernest, 2003; Rolf, 2003; Charnov and Morgan, 2006; Bielby et al., 2007). Except for Kurta and Kunz (1987), Kunz and Stern (1995), Hayssen and Kunz (1996), Kunz and Hood (2000), and Barclay and Harder (2003), size at birth and postnatal growth in bats have seldom been considered in an ecological, evolutionary, or lifehistory context. Despite the various published summaries of size at birth (Kleiman and Davis, 1979; Tuttle and Stevenson, 1982; Kurta and Kunz, 1987; Hayssen and Kunz, 1996; Kunz and Hood, 2000; Barclay and Harder, 2003) and postnatal growth in bats (Orr, 1970; Kleiman and Davis, 1979; Tuttle and Stevenson, 1982; Kunz and Stern, 1995, Kunz and Hood, 2000), few studies have considered intrinsic and extrinsic factors that could infl uence variation in these traits. In this chapter, we provide an overview of studies on size and developmental state at birth (Fig. 14.1A) and postnatal growth and development (Fig. 14.1B), review methods for assessing these traits, identify research needs, propose hypotheses, and suggest directions for future study. Methods for Assessing Size at Birth and Postnatal Growth and Development in Bats