Raw data from: Environmental variation structures reproduction and recruitment in long-lived mega-herbivores: Galapagos Giant Tortoises

Understanding drivers of vital rates is important for testing life history theory, predicting population dynamics, and guiding conservation. Migratory, long-lived animals are important to life history theory because they present an extreme among trade-offs in vital rates: delayed maturity, low fecundity, variable recruitment rates, and long generation times. Understanding how vital rates respond to environmental variation has been elusive for such species because of difficulties in studying wide-ranging animals over extended periods. Populations that live on elevation gradients can provide tractable study systems because considerable environmental change occurs over small geographic distances. Galapagos tortoises are an iconic example; they are long-lived, migrate seasonally, face multiple anthropogenic threats, and have cryptic early life history stages for which vital rates are unknown. From 2012–2021, we studied the reproductive ecology of two species of Galapagos tortoises along ele..., Study site
The Galapagos Islands straddle the equator in the eastern Pacific ca. 1000km west of Ecuador. This volcanic archipelago consists of some 129 islands, including 13 large islands (over 1km2, Fig. 1), the oldest of which are ca. 4M and youngest < 0.5M (Poulakakis et al. 2012). The climate is characterized by a hot wet season from January to May, and a cool dry season for the rest of the year (Trueman and d'Ozouville 2010). However, during the “dry” season, persistent cloud cover results in humid upland conditions on the windward (southern) slopes of the larger islands (Colinvaux 1984). Vegetation patterns are driven by rainfall and substrate, which are largely determined by aspect, elevation, and lava flows.
Our study focused on Santa Cruz Island (Fig. 1), which rises to 860m elevation with a surface area of 986km2 (Snell et al. 1996), one of nine islands Giant tortoises are believed to have currently or previously occupied (Caccone et al. 2002). The island hosts the largest ...,