family reunion "Eurasian Griffon Vultures" by Noor Hussain Via Flickr: Griffon vultures have been used as model organisms for the study of soaring and thermoregulation. The energy costs of level flight tend to be high, prompting alternatives to flapping in larger birds. Vultures in particular utilize more efficient flying methods such as soaring. Compared to other birds, which elevate their metabolic rate to upwards of 16 times their basal metabolic rate in flight, soaring griffon vultures expend about 1.43 times their basal metabolic rate in flight. Griffon vultures are also efficient flyers in their ability to return to a resting heart rate after flight within ten minutes. As large scavengers, griffon vultures have not been observed to seek shelter for thermoregulation. Vultures use their bald heads as a means to thermoregulate in both extreme cold and hot temperatures. Changes in posture can increase bare skin exposure from 7% to 32%. This change allows for the more than doubling of convective heat loss in still air. Griffon vultures have also been found to tolerate increased body temperatures as a response to high ambient temperatures. By allowing their internal body temperature to change independently of their metabolic rate, griffon vultures minimize their loss of water and energy in thermoregulating. One study in particular (Bahat 1995) found that these adaptations have allowed the Griffon vulture to have one of the widest thermal neutral zones of any bird. It declined markedly throughout the 19th–20th centuries in much of Europe, North Africa and the Middle East, mainly due to direct persecution and "bycatch" from the poisoned carcasses set for livestock predators (Snow and Perrins 1998, Ferguson-Lees and Christie 2001, Orta et al. 2015). In some areas a reduction in available food supplies, arising from changes in livestock management practices, also had an impact (Ferguson-Lees and Christie 2001, Orta et al. 2015). It is very highly vulnerable to the effects of potential wind energy development (Strix 2012) and electrocution has been identified as a threat (Global Raptors Information Network 2015). Non-steroidal anti-inflammatory drugs (NSAIDs) used for veterinary purposes pose a threat to this species. One case of suspected poisoning caused by flunixin, an NSAID, was recorded in this species in 2012 in Spain (Zorrilla et al. 2015). Diclofenac, a similar NSAID, has caused severe declines in Gyps vulture species across Asia.