Predator odours as reproductive inhibitors for Norway rats

We examined the influence of predator odor on reproductive output of Norway rats (Rattus norvegicus). Naive laboratory rats responded to predator chemical cues with reduced litter sire and skewed sex ratio. We found that exposure to predator urine had its greatest effect on implantation and maintenance of implantation when predator urine was applied to the bedding of rats during the first third of gestation. Based on the physical appearance of corpora lutea and uterine implantation scars, we found that the reduction in litter sire was due to resolution of the embryos during the early part of gestation. Subsequently, we discovered that the reduction in litter sizes in rats exposed to predator urine could be attributed to suppressed progesterone levels affecting implantation of embryos. Chronically high corticoslerone levels did not suppress reproductive output. Suppression of reproduction also occurred when rats were exposed to urine of conspecifics housed under high population densities. The evolutionary adaptive response for reduced litter sire is to produce high-quality offspring in an environment where food resources are scarce. The fact that rats respond to certain chemical signals in predator urine in a similar fashion may be fortuitous, and may have more to do with the coincidence that the urine contains similar cues resulting from protein digestion in carnivores and protein catabolism in nutritionally deprived rodents, rather than specific predator-prey adaptations

Phylogeographic structure of the Common hamster (Cricetus cricetus L.): Late Pleistocene connections between Caucasus and Western European populations.

The Common hamster (Cricetus cricetus) is one of the most endangered mammals in Western and Central Europe. Its genetic diversity in Russia and Kazakhstan was investigated for the first time. The analysis of sequences of an mtDNA control region and cytochrome b gene revealed at least three phylogenetic lineages. Most of the species range (approximately 3 million km2), including central Russia, Crimea, the Ural region, and northern Kazakhstan), is inhabited by a single, well-supported phylogroup, E0. Phylogroup E1, previously reported from southeastern Poland and western Ukraine, was first described from Russia (Bryansk Province). E0 and E1 are sister lineages but both are monophyletic and separated by considerable genetic distance. Hamsters inhabiting Ciscaucasia represent a separate, distant phylogenetic lineage, named "Caucasus". It is sister to the North phylogroup from Western Europe and the contemporary phylogeography for this species is discussed considering new data. These data enabled us to develop a new hypothesis to propose that in the Late Pleistocene, the continuous range of the Common hamster in the northern Mediterranean extended from the central and southern parts of modern France to the Caucasus; however, its distribution was subsequently interrupted, likely because of climate change

List of samples localities.

<p>Point numbers correspond to <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0187527#pone.0187527.g001" target="_blank">Fig 1</a>.</p

Cladogram resulting from Bayesian phylogenetic analysis of haplotypes of concatenated sequences of <i>cytb</i> gene and control region for hamsters within the investigated area.

<p>Support values are given if they exceeded 0.5 for nodes that included three or more haplotypes. For GenBank accession numbers see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0187527#pone.0187527.t002" target="_blank">Table 2</a>.</p

The hypothetical ranges of the Common hamster hyplogroups: Vertical hatching–Late Pleistocene Northern Mediterranean; horizontal hatching–south-western LGM refugium; filled with colors–modern (mid-20th century).

<p>Note: Atlantic ocean, Mediterranean, Black and Azov sea max. regression, Caspian sea max. transgression coast line shown with the dashed line.</p

Sample distribution map.

<p>Bryansk Province in Western Russia is indicated by a square, localities from the Ciscaucasian area by triangles, and the others by circles. In the breakout: Nalchik City is shown by dark blue, the Nalchik surrounds (restricted by 25-km radius) by light blue, Kislovodsk by red, and other localities by yellow.</p

Divergence time (kya) between the Common hamsters phylogenetic lineages as evaluated based on suggested (1) <i>Tscherskia triton and (Cricetulus migratorius + Allocricetulus eversmanni + Cricetus cricetus)</i> clade and (2) Pannonia and North-type lineages separation time.

<p>Divergence time (kya) between the Common hamsters phylogenetic lineages as evaluated based on suggested (1) <i>Tscherskia triton and (Cricetulus migratorius + Allocricetulus eversmanni + Cricetus cricetus)</i> clade and (2) Pannonia and North-type lineages separation time.</p

Phylogram resulting from Bayesian phylogenetic analysis of 904 bp cyt<i>b</i> gene fragment haplotypes.

<p>Support values are given if they exceeded 0.5 for nodes that included three or more haplotypes.</p