All things considered? Alternative reasons for hamster extinction

Abstract

In 2002 a pest biologist (LEIRS 2002) calculated the survival chances of the European hamster (Cricetus cricetus) according to data provided by participants of the meeting of the International Hamster Workgroup in Tongeren. His model was based predominantly on demographic data as birth rates and predicted that the European hamster will be extinct in Western Europe within the next 50 years. Since then, the mean number of litters females raise in a year has diminished from 2-3 to 1-2. It is thus to be feared that the remaining time is only half as long as predicted and extinction might occur around 2030. However, since then hamster protection measures have improved considerably and two major milestones have been reached: (1) we are able to breed captive hamsters in a sufficient number and (2) most released hamsters survive long enough to reproduce once. Thus, at the present state we can claim that the hamster won.t go extinct as long as such breeding and releasing programs are in place. However, we haven.t achieved a state yet at which it is clear that the hamster will survive with its own means when such programs are stopped. To work on this will be the task of the coming years. This review might be a starting point for that. It reflects on which other factors possibly impair the survival of European hamster populations besides some aspects of modern agriculture, thus it searches for parameters which are not yet considered in conservation programs. Historical data as well as observations and research data from other species are reviewed. Additionally, new insights from the subterranean life of European hamsters in outdoor terrariums are presented, which suggest that the soil as habitat might need more attention in conservation. However, this conjecture can provide only new ideas, which still have to be confirmed by research. The intention is to spark a lively discussion on such potential alternative reasons for the decline of European hamsters, whether some of them are worth being investigated and whether we overlooked something. There is not much time left.

Dramatic global decrease in the range and reproduction rate of the European hamster Cricetus cricetus

“…One hypothesis is that steadily declining population densities increasingly failed to stimulate reproduction. There is a striking similarity between the fate of passenger pigeons and the decline of European hamsters (Hutterer & Geiger-Roswora 1997, Monecke 2013. The decline of hamsters might have started with overhunting leading to decreasing population densities, which negatively affected the reproduction rate.…”

“…It is very likely that analogous to circadian rhythms (Ralph & Menaker 1988, Monecke et al 2011b, the timing of circannual rhythms has a heritable component with early-and late-reproducing geno types (Monecke 2013). In this case, fur trapping would have caused a strong selection pressure against early-reproducing animals, which may have led to a progressive decline of animals carrying the early-reproducing genotype.…”

“…Finally, the onset of the decline of the European hamster also makes it appear highly unlikely that modern agriculture is one of the main causes, since modern farming methods started much later than the decline of European hamsters. In Germany, hamsters declined as early as the 1920s (Eisentraut 1928, Petzsch 1933, Monecke 2013in Hungary between 1960and 1980(Bihari 2003; and in the Omskaya oblast in Siberia in the late 1950s (Sidorov et al 2011).…”

Diets derived from maize monoculture cause maternal infanticides in the endangered European hamster due to a vitamin B3 deficiency

“…The European hamster (Cricetus cricetus)-critically endangered in Europe [21][22][23]-is particularly threatened by the expansion of wheat and maize monocultures in Western Europe [22,24]. The highly fluctuating food availability (with crop rotation and harvest) associated with the strong seasonality of the species (which hibernates from October -April and reproduces from April -September) put it at high risk of facing periods of food scarcity, even during the reproductive period (e.g.…”

The genetic characterization of an isolated remnant population of an endangered rodent (Cricetus cricetus L.) using comparative data: implications for conservation

“…between the Pannonia and West lineages (Smulders et al 2003) or between the Pannonia and Central lineages (Neumann et al , 2005, and results of this study); (2) reports exist showing that the contemporary hamsters have reduced fitness relative to those alive prior to the population crisis (e.g. Pucek 1981; Monecke et al 2013), thus the beneficial effect of proposed outcrossing, such as heterosis, may be observed, and (3) biological importance of postulated ESUs is not always clearly defined and understood, and subspecies designation is not broadly accepted Banaszek et al 2009Banaszek et al -2010Schröder et al 2014). In conclusion, if the decline in genetic diversity is strictly due to neutral processes in JW, introducing a new genetic variant would be beneficial.…”