Recent cetacean taxonomic changes and conservation action

Taxonomic uncertainty continues to be an impediment to efficient conservation, even for large and charismatic animals such as whales and dolphins. This is exemplified by several discoveries in the last few months alone: a new species of great whale was described in the Gulf of Mexico (Rosel et al., 2021); there was the discovery of a beaked whale that is likely to be an undescribed species from the coast of Mexico (https://news.mongabay.com/2020/12/whale-of-a-find-scientists-spot-beaked-whale-believed-to-be-a-new-species); and, most recently, the South Asian river dolphin species (Platanista gangetica), was split into two separate and highly endangered species, the Indus and Ganges river dolphins (Platanista minor, and Platanista gangetica, respectively) (Braulik et al., 2021). These cases reveal not only how much we still have to learn about whales and dolphins but how difficult it is to gather enough information to able to understand and scientifically describe them, even for dolphin species found in rivers, with comparatively limited distributions, and living amongst millions of humans. The river dolphin study, for example, took 20 years to complete, years that also saw the ranges of both species decline substantially.

Although describing species is not equivalent to saving them, there is a link between increased taxonomic knowledge and increased conservation attention (Morrison et al., 2009). Species form the basis for almost all national and international wildlife legislation, environmental management, conservation planning, and allocation of funding (Mace, 2004). Effective conservation therefore depends on strong and well-founded science based on taxonomy and systematics (Mace, 2004). It is important to recognize that although it is imperative that taxonomic decisions are based on sound science, these decisions also have far-reaching political consequences and a significant impact on management and conservation on the ground. For example, a comprehensive review showed that the splitting of species frequently results in increased protection (Morrison et al., 2009).

As two of the most endangered of all cetacean species, with each numbering only a few thousand individuals and listed as Endangered on the International Union for Conservation of Nature (IUCN) Red List, the Indus and Ganges river dolphins are both in grave need of increased efforts to improve their habitat and reduce threats. Indus River dolphins have been increasing in abundance in recent years, but with more than 80% of their habitat gone, the remaining distribution is vulnerable to climate change, coupled with increased demand for water and rising levels of pollution (Braulik et al., 2015). By contrast, Ganges River dolphins, although more numerous and with a larger range than the Indus river dolphins, are facing a formidable array of threats, in the form of large infrastructure projects that will modify their already depleted and degraded habitat into major dredged shipping lanes (Kelkar, 2017). In the face of such overwhelming transformation, disturbance, and degradation of dolphin habitat, it is unlikely that any mitigation measures will be able to prevent a continued or accelerating decline. These unique blind dolphins may serve as sentinels, showing the value and importance of healthy, undisturbed, connected rivers, both for humans and wildlife, before it is too late.