In aid of (re)discovered species: maximizing conservation insights from minimal data

Abstract

New species discoveries or the rediscovery of species once considered extinct or extirpated is good news, and yet prospects for long-term survival may be bleak if remnant populations are small and isolated. Because (re)discovered species are commonly rare or cryptic, data to inform appropriate conservation actions are usually sparse. We demonstrate how to make the most of available data, using the recent rediscovery in Ghana of sitatunga Tragelaphus spekei as an illustrative case study. Sitatunga were thought extinct in Ghana for over 50 years, but were 'rediscovered' by science in Avu Lagoon in 1998. Little is known about this species, especially West African populations, given its cryptic nature and inaccessible wetland habitat. Our approach to maximizing insights given limited data first paired observations of occurrence with landscape characteristics derived from open-access remote sensing data, creating the first ever habitat suitability model for sitatunga. This model then served to: (1) elucidate habitat preferences; (2) assess possible existence and connectivity of remnant populations elsewhere in Ghana; and (3) estimate maximum total and effective population size. Moreover, the timing of occurrence sightings provided insights into behavior. Sitatunga sightings were rare, heavily male-biased and mostly occurred between 6 pm and 6 am. Suitable habitat was limited, suggesting that habitat in and near Avu Lagoon is insufficient to ensure long-term population viability, and the existence of other, connected populations in Ghana is improbable. Without continued protection, and possibly additional interventions to augment population numbers or gene flow, the sitatunga in Avu Lagoon will likely go extinct. Our case study demonstrates the conservation challenges associated with the rediscovery of relict populations, and the utility of applying tools such as habitat suitability models to sparse data. Moreover, our research stresses the need to implement immediate conservation action upon species (re)discoveries to prevent (regional) extinction.