Health assessment of Conolophus subcristatus, Conolophus pallidus, and C. subcristatus X Amblyrhynchus cristatus hybrid (Galápagos land iguanas)

Abstract

The land iguanas, Conolophus pallidus and Conolophus subcristatu are large and charismatic lizards endemic to the Galápagos archipelago, but little information exists on their normal health parameters. The former is restricted to Santa Fe island, while C. subcristatus inhabits the islands of the central and western region of the archipelago. Both species are classified as vulnerable by the IUCN Red List of Threatened Species. As part of a population health assessment authorized by the Galápagos National Park, wild adult iguanas from three islands (North Seymour, South Plazas, and Santa Fe) were captured in July 2018. Data from a single C. subcristatus X Amblyrhynchus cristatus hybrid captured on South Plazas is also included. We analyzed blood samples drawn from 52 healthy wild adult land iguanas captured on three islands. An iSTAT portable blood analyzer was used to obtain values for pH, lactate, pO2, pCO2, HCO3-, sO2%, hematocrit, packed cell volume (PCV), hemoglobin Na, K, iCa, and glucose. Standard laboratory hematology techniques were employed for PCV determination; resulting values were also compared to the hematocrit values generated by the iSTAT. Body temperature, heart rate, respiratory rate, and body measurements were also recorded and compared to previously published data for the marine iguana (Amblyrhynchus cristatus), which shares a common ancestor with the land iguana. The data reported here provide preliminary baseline values that may be useful in comparisons between captive and wild populations, between wild populations, and in detecting changes in health status among Galápagos land iguanas affected by anthropogenic threats, climate change, or natural disturbances.

Fig 1. The interspecific population comparison among land iguanas from the three studied islands showed large and highly significant differences in body size (SVL: Kruskal Wallis Test: X² = 17.484, df = 2, p< 0.001) and weight (Kruskal Wallis Test: X² = 21.919, df = 2, p-value < 0.001).

Fig 2. Linear regression and correlations of iSTAT hematocrit and hemoglobin with C. pallidus body size (SVL = Snout vent length).

Linear regression models: BODY MASS (KG) = -6.60088 + 0.23858 (S_E = 0.03744)*SVL (t = 6.372, p = 4.11e-06); HctiSTAT (%) = 0.4580 + 0.6445 (S_E = 0.2034)*SVL (t = 3.168, p = 0.00507); Hb (g/L) = 0.10100 + 0.22012 (S_E = 0.06957)*SVL (t = . 3.164. , p = 0.00511). S_E refers to standard error.