No abstract

Once cornered by a predator, prey can try to intimidate the assailant or repel it, with irritating sprays for example. If seized, they may scratch, bite or struggle to cause the predator to release its grip. At the other extreme, they can adopt passive behaviours such as death feigning (DF, i.e. thanatosis). DF is observed widely across the animal kingdom; it usually involves a combination of displays such as immobility, supination, leg‐folding, mouth opening and release of nauseating secretions. When displaying DF, individuals are highly vulnerable and effectively bet on the attitude of the predator; this risky choice is presumably under positive selection. We explored how propensity for DF varies among and within populations of dice snakes (Natrix tessellata). We also considered the influence of sex, body size, reproductive status, colour morph and presence of injuries (N = 2760 snakes; five populations). DF propensity differed among populations, possibly due to variation in local predation pressures. Larger snakes displayed DF more frequently and carried more signs of probable past predation attempts (scars and recent injuries). We found no sex effect on antipredator behaviour. Gravid females used DF less frequently compared with non‐gravid females. Differential expression of DF across populations, body sizes and reproductive status suggests that this complex behaviour was selected to respond to environmental and intrinsic factors. Future studies should explore which elements affect duration, intensity and success of DF in defence against various predators.

This paper gives the first record of round goby Neogobius melanostomus Pallas, 1814 (Pisces: Gobiidae) in Bosnia and Herzegovina.

Two new populations of the European mudminnow (Umbra krameri Walbaum, 1792) were discovered in the Sava River system, one in its middle part (Bosnia and Herzegovina) and the other in a tributary to the Kupa River (Croatia). The Croatian population is the most upstream mudminnow discovery in the Sava River system known to date. The genetic structure of the newly recorded mudminnow populations was examined using mitochondrial DNA and microsatellite loci. By adding these new populations to the analysis of the population genetic structure of mudminnow from the Sava River system, previously unresolved relationships between the populations from the upper and the lower Sava were clarified: the middle Sava populations were shown to be well outside the hybridisation zone with the Danubian clade, meaning the upstream boundary of this zone is confined to the lower Sava. The results also suggest that mudminnow populations in the Sava River system are less isolated than previously believed. Namely, intermediate gene-flow was detected when comparing the uppermost Sava population with the lower Sava populations. Taking these results into account, appropriate guidelines are proposed to preserve mudminnow populations from the Sava River system.

One extremely large leech specimen of Trocheta haskonis Grosser, 2000, reaching almost 190 mm when contracted, was collected in an underground vault constructed out of concrete in the village Prijakovci in the north-western part of Bosnia and Herzegovina. This finding indicates that one of the largest European leech species can colonize also small artificial habitats like a utility vaults, possible also subway tunnels and storm drains.