Homing and home-site fidelity in rock-dwelling cichlids (Pisces: Teleostei) of Lake Malawi,Africa

Synopsis Existence of home site fidelity and homing ability was established for Pseudotropheus aurora. Territorial males stayed up to 1 1/2 years within the same territories. Females showed long-term fidelity to certain places. Transplantation experiments revealed that P. aurora males home over distances of up to at least 2500 m but would not cross deep water. The territorial males of five other sympartic species returned from 1000 m to their territories. The mechanisms and functions of homing in cichlids are discussed.     

Cycling of amino-nitrogen between shoots and roots in wheat seedlings

Summary One part of a split root system of wheat seedlings received full nutrient solution with¹⁵N-nitrate, the other received an identical solution with unlabelled nitrate. Appearance of labelled amino compounds was measured in the xylem sap exuding from roots not supplied directly with¹⁵N-nitrate after removal of the¹⁵N-nitrate-fed roots. This material indicates cycling of nitrogen from the shoots and through the roots. About 60 per cent of the nitrogen in the xylem appears to be cycling in this way.     

Biogeography and incipient speciation in Ophryotrocha labronica (Polychaeta, Dorvilleidae)

Crossing experiments were conducted between the Naples I (NI) strain of Ophryotrocha labronica labronica, three strains of O. l. pacifica from Japan (M3), Hawaii (WH) and Los Angeles (LA), two strains of O. labronica from Australia and one from an unknown origin, discovered in a Moscow aquarium, to determine the relationships between the European and Pacific subspecies, and the newly discovered strains. Previously published data combined with new results revealed several stages in the process of speciation within the sibling group. Interpopulation crosses yielded an increased sex ratio that appears to be positively related to genetic distance and to the sex ratio of the parent strains. Fecundity data demonstrated that the three northern Pacific strains are more closely related to each other than to any other strain, confirming that they are a valid subspecies, and indicate that they are the result of natural distribution. The strain of unknown origin as well as the Australian strains clearly belong to O. l. labronica. Its isolated presence in the South Pacific may be a remnant of an earlier wider distribution or an introduction of the Mediterranean population, as the life histories of Ophryotrocha species have made them prime candidates for anthropogenic dispersals.     

Roadway mortality of barn owls in Idaho,USA

We examined the temporal, spatial, and demographic factors that influenced roadway mortality of barn owls (Tyto alba) along a 248-km stretch of Interstate 84 in southern Idaho using systematic road surveys. Counts of dead animals from surveys can be underestimated because of sampling biases; therefore, we also conducted experiments to assess the effects of search and removal bias on the estimates of roadway mortality of owls. We conducted surveys every 2 weeks over a 2-year period and detected 812 dead barn owls (unadjusted mortality rate of 1.64 owls/km/yr). After adjusting this estimate for search and removal bias, we documented mortality rates of up to 5.99 owls/km/year. Owl mortality was not random in relation to sex, age class, or location along the highway. Females and juveniles, which represent individuals more likely to disperse long distances, were killed more frequently than males and adults. During the nonbreeding season, owls were killed more often near agricultural lands than in shrub-steppe, but this pattern was not apparent during the breeding season. Owls were also killed more often on portions of the roadway closer to the Snake River canyon, perhaps because of the availability of nest and roost sites. Mortality rates differed markedly between the 2 years of study, which could have been related to variability in weather and its subsequent effect on owl productivity. Our data suggest that barn owls in this region may not persist under this level of mortality without significant immigration or management. Thus, roadway management to reduce or prevent owl use of roadways, reduce rodent populations near major roads, alert motorists to the presence of owls, or otherwise reduce the chances that vehicles and owls collide would improve barn owl survival and population persistence. © 2012 The Wildlife Society.     

Maternal grouping as a defense against infanticide by males: evidence from field playback experiments on African lions

Female lions roar in order to stay in contact with their pridematesand to defend their territory against other prides. In doingso, however, they risk attracting die attention of potentiallyinfanticidal nonresident males. We used playback experimentsto demonstrate that nonresident males are indeed specificallyattracted to female roars, approaching the roars of female,but not male, conspecifics. However, diere was also evidencediat males adjust their behavior according to the probabilitythat they might execute a successful takeover. Alien male lionswere more reluctant to approach playbacks of three females roaringdian of a single female roaring; single males were more reluctantdian pairs to approach female roars; and old males were morereluctant than younger males to approach female roars. Previousobservational studies have shown diat female lions living ingroups are more successful than singletons at defending theircubs in direct interactions widi potentially infanticidal males.Our results suggest that maternal groups may also, by roaringin chorus, minimize the chances that diese encounters occurat all.     

Intraspecific interactions influence size specific depth distribution in Cottus bairdi

Synopsis We tested depth selection by different sizes of mottled sculpin, Cottus bairdi, in a southern Appalachian stream. Field observations indicated that, during one hour periods, both small (<50 mm SL) and large (≥55 mm SL) individuals move within an area less than 0.50 m². Individuals of both sizes, placed in field enclosures, preferred deep microhabitat. When large fish were placed in cages with small fish, small fish initially spent more time in slope and shallow microhabitats. Average interfish distances were not correlated with their absolute size differences, suggesting C. bairdi interactions may involve both predation and competition. In streams, size-related differences in microhabitat depth may result more from intraspecific interactions than from size-specific depth preferences.     

Argentine ant foraging activity and interspecific competition in complete vs. queenless and broodless colonies

Introduction experiments may prove useful in understanding the mechanisms underlying the successful establishment of invasive ant species into new areas. These manipulative introductions could be particularly helpful in exploring the interactions between invasive species and the local fauna and flora. However, the inherent risk of accidental establishment in such experiments poses unacceptable ethical concerns. Some of the worst invasive species are tramp ant species, which can adversely affect biodiversity and community structure after establishment. We conducted laboratory and field experiments investigating a safe methodology for carrying out introduction experiments using the sterile workers of the invasive Argentine ant, Linepithema humile, as a model. We found no difference in foraging rate between worker-only colonies of L. humile and complete colonies, containing queens, workers and brood. Worker-only L. humile colonies showed the same exploitative and interference ability as complete colonies in bait dominance trials with the odorous house ant, Tapinoma sessile, in both laboratory and field trials. We suggest that for those invasive ant species with sterile workers, worker-only colonies may be substituted for complete colonies in short-term field experiments in new areas. Received 18 January 2007; revised 19 June 2007; accepted 22 June 2007.     

Laboratory experiments on the schooling and feeding behaviour of Trichogaster fasciatus (Pisces: Perciformes)

Laboratory experiments were performed on the schooling and feeding behaviour of Trichogaster fasciatus . There was a tendency on the part of individuals of similar size to school together; the instinct being stronger in younger specimens. Unavailability of similar-sized individuals led to schooling by members of different size-groups. Column feeding was exhibited by the fish. While feeding at the bottom, the fishes formed angles varying from 30°90°. Larger individuals formed a right angle more often than younger members of the species. Optimum degree of crowding seemed necessary for active feeding as confinement of single individual, or overcrowded condition, both resulted in a decline of feeding activity.