Sir

Your News Story “Animal-rights group sues over ‘disturbing’ work on sea lions” (Nature 436, 315; 200510.1038/436315a) shows how wildlife researchers face escalating criticism over their use of invasive procedures to collect ecological data for population management. Although we appreciate and agree that all due consideration should be paid to the welfare of study animals, we argue that invasive research techniques are sometimes inevitable and integral parts of animal research in the global pursuit of biodiversity conservation.

The branding of seals is one technique criticized for being an invasive conservation tool. The technique has, however, provided important insights on juvenile survival that help to explain the processes involved in recent population declines — and a long-term programme of branding southern elephant seals (Mirounga leonina) on Macquarie Island, Australia, has shown that it has no discernable long-term impact on survival or condition (C. R. McMahon et al. J. Wildl. Mgmt, in the press).

The issue of branding on Macquarie Island became so controversial that the programme was suspended indefinitely (J. A. Jabour-Green and C. J. A. Bradshaw J. Nat. Conserv. 12, 25–39; 2004). Similar intervention has occurred in conservation research on two endangered species: New Zealand sea lions (Phocarctos hookeri) in New Zealand and Steller sea lions (Eumetopias jubatus) in the United States. Such political interference on the basis of animal-welfare issues is difficult to justify, considering that, in the United States alone, some 36 million beef cattle are hot- or cryo-branded each year, according to the US Department of Agriculture.

Effective conservation of species is urgently needed in the current biodiversity crisis. To this end, we urge scientists and welfare lobbyists to combine their efforts and consider objectively the pertinent issues balancing the desperate need for sound biological information with animal welfare.