One-fifth of all vertebrate species worldwide are threatened with extinction and many have undergone declines. Several rabbit species also face similar circumstances and have become increasingly threatened with habitat loss. A new study, currently in press in Biological Conservation, identifies the provision of food supplements as a conservation measure to enhance rabbit survival.

Last October a study published in Science listed one-fifth of the world's vertebrates as ''Threatened''. Moreover, this assessment, to which 174 scientists have contributed, clearly states that this figure is increasing, with an average 52 species of mammals, birds and amphibians moving one International Union for Conservation of Nature (IUCN) Redlist category closer to extinction each year. The main threats faced by these groups are agricultural expansion, logging, overexploitation, and invasive alien species.

Rabbits have not been spared this drive to extinction, with intensified agricultural practices and land use changes reportedly suggested as the reason for the decline of several species, both in Europe and the US.

The New England Cottontail (Sylvilagus transitionalis) is a rabbit species of New England, which populations have been reduced to 86 percent over the past 50 years, and to five disjunct populations that span less than 15% of the historic range of the species.

This species is dependent upon forests and shrubland, which area has become increasingly reduced and fragmented, forcing the rabbits to move larger distances and to forage out of these patches to find food, and thus making them more visible to predators. This leads to increased likelihood of predation by coyotes and foxes.

Researchers from the Department of Natural Resources and The Environment, from the University of New Hampshire in Durham, evaluated the use of supplemental food as an approach to improve overwinter survival rates.

Rather than using the increasingly threatened New England Cottontail, they used eastern cottontails (Sylvilagus floridanus), as a research surrogate, because this species is readily available and has similar habitat requirements to New England cottontails.

Transmitters were attached to rabbits to monitor their movement and feeders where periodically supplied with commercial rabbit chow.

This strategy increased survival rates from 32 per cent in unfed rabbits to 70 per cent for those which had access to feeders, leading the researchers to conclude that supplemental feeding may improve survival of the remaining New England Cottontails.

With several species worldwide facing extinction, as the activities of our own species remain the unique cause of the current mass extinction that characterises the present chronological period – the Anthropocene, the long-term viability of such conservation measures is an important issue. While such techniques may be effective for rabbits, and several other charismatic species, conservation of the habitat is essential for maintaining biodiversity, of which hundreds of thousands of species (mainly invertebrates) remain unknown to science.