The ability to associate environmental cues with valuable resources strongly increases the chances of finding them again, and thus memory often guides animal movement. For example, many temperate region amphibians show strong breeding site fidelity and will return to the same areas even after the ponds have been destroyed. In contrast, many tropical amphibians depend on exploitation of small, scattered and fluctuating resources such as ephemeral pools for reproduction. It remains unknown whether tropical amphibians rely on spatial memory for effective exploitation of their reproductive resources. Poison frogs (Dendrobatidae) routinely shuttle their tadpoles from terrestrial clutches to dispersed aquatic deposition sites. We investigated the role of spatial memory for relocating previously discovered deposition sites in an experimental population of the brilliant-thighed poison frog, Allobates femoralis, a species with predominantly male tadpole transport. We temporarily removed an array of artificial pools that served as the principal tadpole deposition resource for the population. In parallel, we set up an array of sham sites and sites containing conspecific tadpole odour cues. We then quantified the movement patterns and site preferences of tadpole-transporting males by intensive sampling of the area and tracking individual frogs. We found that tadpole-carrier movements were concentrated around the exact locations of removed pools and most individuals visited several removed pool sites. In addition, we found that tadpole-transporting frogs were attracted to novel sites that contained high concentrations of conspecific olfactory tadpole cues. Our results suggest that A. femoralis males rely heavily on spatial memory for efficient exploitation of multiple, widely dispersed deposition sites once they are discovered. Additionally, olfactory cues may facilitate the initial discovery of the new sites.

Cross-boundary transfers of nutrients can profoundly shape the ecology of recipient systems. The common hippopotamus, , is a significant vector of such subsidies from terrestrial to river ecosystems. We compared river pools with high and low densities of to determine how subsidies shape the chemistry and ecology of aquatic communities. Our study watershed, like many in sub-Saharan Africa, has been severely impacted by anthropogenic water abstraction reducing dry-season flow to zero. We conducted observations for multiple years over wet and dry seasons to identify how hydrological variability influences the impacts of During the wet season, when the river was flowing, we detected no differences in water chemistry and nutrient parameters between pools with high and low densities of Likewise, the diversity and abundance of fish and aquatic insect communities were indistinguishable. During the dry season, however, high-densitys pools differed drastically in almost all measured attributes of water chemistry and exhibited depressed fish and insect diversity and fish abundance compared with low-density pools. Scaled up to the entire watershed, we estimate that in this hydrologically altered watershed reduces dry-season fish abundance and indices of gamma-level diversity by 41% and 16%, respectively, but appears to promote aquatic invertebrate diversity. Widespread human-driven shifts in hydrology appear to redefine the role of , altering their influence on ecosystem diversity and functioning in a fashion that may be more severe than presently appreciated.

Among vertebrates, comparable spatial learning abilities have been found in birds, mammals, turtles and fishes, but virtually nothing is known about such abilities in amphibians. Overall, amphibians are the most sedentary vertebrates, but poison frogs (Dendrobatidae) routinely shuttle tadpoles from terrestrial territories to dispersed aquatic deposition sites. We hypothesize that dendrobatid frogs rely on learning for flexible navigation. We tested the role of experience with the local cues for poison frog way-finding by (i) experimentally displacing territorial males of Allobates femoralis over several hundred metres, (ii) using a harmonic direction finder with miniature transponders to track these small frogs, and (iii) using a natural river barrier to separate the translocated frogs from any familiar landmarks. We found that homeward orientation was disrupted by the translocation to the unfamiliar area but frogs translocated over similar distances in their local area showed significant homeward orientation and returned to their territories via a direct path. We suggest that poison frogs rely on spatial learning for way-finding in their local area.

Knowing animals' gut retention time (GRT) for important food items is critical when using non‐invasive studies based on faecal remains, e.g. when analysing nutritive quality of food, or relating diet or behaviour to movements. We analysed GRT in six captive brown bears Ursus arctos, after feeding on either berries (a mixture of bilberry Vaccinium myrtillus and lingonberry V. vitis‐idaea) or animal carcasses (either reindeer Rangifer tarandus, European rabbit Oryctolagus cuniculus, domestic pig Sus scrofa domestica, cattle Bos taurus or horse Equus ferus caballus). Median GRT50% (i.e. when 50% of all faeces containing experimental food had been defecated) was 5 hours and 47 minutes (1st and 3rd quartiles = 4 hours and 36 minutes and 7 hours and 3 minutes; N = 20) after feeding on berries and 14 hours and 30 minutes (1st and 3rd quartiles = 10 hours and 9 minutes and 16 hours and 57 minutes; N = 20) after feeding on carcasses. Median GRTmin (i.e. first defecation comprised of experimental food) was 3 hours and 5 minutes (1st and 3rd quartiles = 1 hour and 51 minutes and 4 hours and 12 minutes; N = 21) for berries and 8 hours and 2 minutes (1st and 3rd quartiles = 6 hours and 14 minutes and 10 hours and 44 minutes; N = 20) for carcasses. Median GRTmax (i.e. last defecation comprised of experimental food) was 15 hours and 27 minutes (1st and 3rd quartiles = 11 hours and 36 minutes and 17 hours and 16 minutes; N = 21) for berries and 16 hours and 16 minutes (1st and 3rd quartiles = 12 hours and 11 minutes and 17 hours and 27 minutes; N = 20) for carcasses. A carcass diet had 6 hours and 26 minutes ± 1 hour and 56 minutes (SE) longer GRT50% than a berry diet (N = 39), despite low variation in food intake. Activity level, feeding time (midday/midnight), sex, age (subadult/adult), ingested amounts of food, prior food remains processed by the gut (i.e. cumulative faeces weight) and defecation rate did not influence the GRT50%. Our reported GRT estimates are reliable values to be used within research and management to relate diet based on faecal remains to habitat use for common and important food items used by Scandinavian brown bears.

a b s t r a c tOlfactory cues have been investigated in social carnivores, many of which use anal/anogenital gland secretion (AGS) for scent marking. However, little is known about how solitary carnivores, such as ursids, use AGS in communication. We hypothesized that subadult (1-3 years) brown bears (Ursus arctos) have the ability to discriminate between unfamiliar adult male and female AGS. Confrontations, especially with adult males, carry high risks for dispersing subadults, so they benefit from the ability to assess potential threats based on olfactory cues, including sex, enabling them to avoid risky encounters. We presented AGS from free-ranging adult brown bears (male = 10, female = 10) to subadult brown bears (male = 13, female = 7) in outdoor zoo experiments, and predicted that subadults would avoid male more than female AGS. Neither male nor female AGS were avoided, but subadults quickly habituated to female AGS. However, male AGS was investigated more intensively and the subadults delayed revisiting it. Subadult tended to take longer to complete 6 visits to male than female AGS, which indicated sexual discrimination. We suggest that subadults that store information for the purpose of scent matching in future encounters may reduce their potential costs of conflict based on their prior assessment of the likely outcome of the encounter.