Snake prices and crocodile appetites: Aquatic wildlife supply and demand on Tonle Sap Lake, Cambodia

Commercial trade is a major driver of over-exploitation of wild species, but the pattern of demand and how it responds to changes in supply is poorly understood. Here we explore the markets for snakes from Tonle Sap Lake in Cambodia to evaluate future exploitation scenarios, identify entry points for conservation and, more generally, to illustrate the value of multi-scale analysis of markets to traded wildlife conservation. In Cambodia, the largest driver of snake exploitation is the domestic trade in snakes as crocodile food. We estimate that farmed crocodiles consume between 2.7 and 12.2 million snakes per year. The market price for crocodiles has been in decline since 2003, which, combined with rising prices for their food, has led to a reduced frequency of feeding and closure of small farms. The large farms that generate a disproportionate amount of the demand for snakes continue to operate in anticipation of future market opportunities, and preferences for snakes could help maintain demand if market prices for crocodiles rise to pre 2003 levels. In the absence of a sustained demand from crocodile farms, it is also possible that alternative markets will develop, such as one for human snack food. The demand for snakes, however, also depends on the availability of substitute resources, principally fish. The substitutability and low price elasticity of demand offers a relatively sustainable form of consumerism. Given the nature of these market drivers, addressing consumer preferences and limiting the protection of snakes to their breeding season are likely to be the most effective tools for conservation. This study highlights the importance of understanding the structure of markets and the behaviour of consumer demand prior to implementing regulations on wildlife hunting and trade

The influence of social experience on the ontogenetic change in the relation between aggression, fear and display behaviour in black-headed gulls

This study investigated whether changes in motivation of displays, occurring during normal ontogeny in black-headed gulls, Larus ridibundus, are under the influence of social experience. To this end, birds were rearerd either in isolation or in groups of three. In the latter, the birds had social interactions, but did not show agonistic behaviour. The development of overt aggression and display behaviour was tested with a standard stimulus object, namely a stuffed or a live adult conspecific. In several aspects, the change in relation between aggression, fear and display was retarded in the experimental birds compared with that of control birds reared in a large group of at least nine birds. After re-housing in similar large groups, birds reared in isolation showed persistent deviations in frequency and orientation of agonistic and sexual behaviour. It is argued that the changes in motivation of display during ontogeny are influenced by specific experience with agonistic interactions, and may involve learning based on operant conditioning.