Nonmotorized recreation and motorized recreation in shrub‐steppe habitats affects behavior and reproduction of golden eagles (Aquila chrysaetos)

Different forms of outdoor recreation have different spatiotemporal activity patterns that may have interactive or cumulative effects on wildlife through human disturbance, physical habitat change, or both. In western North America, shrub‐steppe habitats near urban areas are popular sites for motorized recreation and nonmotorized recreation and can provide important habitat for protected species, including golden eagles. Our objective was to determine whether recreation use (i.e., number of recreationists) or recreation features (e.g., trails or campsites) predicted golden eagle territory occupancy, egg‐laying, or the probability a breeding attempt resulted in ≥1 offspring (nest survival). We monitored egg‐laying, hatching and fledging success, eagle behavior, and recreation activity within 23 eagle territories near Boise, Idaho, USA. Territories with more off‐road vehicle (ORV) use were less likely to be occupied than territories with less ORV use (β = ?1.6, 85% CI: ?2.8 to ?0.8). At occupied territories, early season pedestrian use (β = ?1.6, 85% CI: ?3.8 to ?0.2) and other nonmotorized use (β = ?3.6, 85% CI: ?10.7 to ?0.3) reduced the probability of egg‐laying. At territories where eagles laid eggs, short, interval‐specific peaks in ORV use were associated with decreased nest survival (β = ?0.5, 85% CI: ?0.8 to ?0.2). Pedestrians, who often arrived near eagle nests via motorized vehicles, were associated with reduced nest attendance (β = ?11.9, 85% CI: ?19.2 to ?4.5), an important predictor of nest survival. Multiple forms of recreation may have cumulative effects on local populations by reducing occupancy at otherwise suitable territories, decreasing breeding attempts, and causing nesting failure. Seasonal no‐stopping zones for motorized vehicles may be an alternative to trail closures for managing disturbance. This study demonstrates the importance of considering human disturbance across different parts of the annual cycle, particularly where multiple forms of recreation have varying spatiotemporal use patterns that create human–wildlife interactions.     

High surface temperatures select for individual foraging in ants

Natural selection favors signals, receptors, and signaling behaviorthat maximize the received signal relative to background noiseand that minimize signal degradation. The physical propertiesof the environment affect rates of attenuation and degradationof the signal, and thus temperature may influence the evolutionand maintenance of volatile chemical signals. We tested this hypothesis in ants, where nest mate recruitment to a food sourceby laying trail pheromones on a surface is a common phenomenon.We collected data on maximal soil surface temperatures duringthe ants' activity and mode of foraging (recruitment or solitary).By using two different comparative methodologies, we demonstrateda relationship between maximal soil temperature at which speciesare active and recruitment behavior (which is hypothesized to be related to the presence or absence of chemical signals).The species that were active at lower temperatures proved tobe those that used chemical signals to recruit nest mates duringforaging. This is also the case when comparing sympatric speciesand thereby controlling for other environmental factors. Moreover,all seven nonrecruiter species developed from recruiter ancestries,which is consistent with our hypothesis because ample evidence suggests a forest and tropical origin for ants. Thus, contraryto previous hypotheses, species that forage individually cannotbe categorically considered primitive, but rather appear tobe derived from recruiter species. Therefore, we conclude thattemperature influences the evolution and/or stability of chemicalsignals in ants by determining the recruitment of nest mates.     

Effects of gaster extract trail concentration on the trail following behaviour of the Argentine ant, Iridomyrmex humilis (Mayr)

In the Argentine ant, optimum trail following to gaster extracts was displayed to 0.1 and 1.0 equivalents/50 cm of circular trail. Trail following to airborne components was demonstrated when ants exhibited normal trail following behaviour while walking 3 or 6 mm below a 0.1 ant equivalent trail. However, at 8 or 12 mm separation, following ceased, indicating that the height of the active space was ca. 6–8 mm. The average horizontal distance from the centre of the trail at which ants exhibited following behaviour increased with concentration to 3–4 mm beyond the applied trail boundaries, indicating both an ability to follow airborne chemicals, and possibly a non-tolerance of excessively high concentration. Activity of 0.1 ant equivalent trails on filter paper declined to about half the original level by four hours; after eight hours, responses were significantly different from, but almost as low as, solvent controls.     

Effect of Trail Bifurcation Asymmetry and Pheromone Presence or Absence on Trail Choice by Lasius niger Ants

During foraging, ant workers are known to make use of multiple information sources, such as private information (personal memory) and social information (trail pheromones). Environmental effects on foraging, and how these interact with other information sources, have, however, been little studied. One environmental effect is trail bifurcation asymmetry. Ants forage on branching trail networks and must often decide which branch to take at a junction (bifurcation). This is an important decision, as finding food sources relies on making the correct choices at bifurcations. Bifurcation angle may provide important information when making this choice. We used a Y‐maze with a pivoting 90° bifurcation to study trail choice of Lasius niger foragers at varying branch asymmetries (0°, [both branches 45° from straight ahead], 30° [branches at 30° and 60° from straight ahead], 45°, 60° and 90° [one branch straight ahead, the other at 90°]). The experiment was carried out either with equal amounts of trail pheromone on both branches of the bifurcation or with pheromone present on only one branch. Our results show that with equal pheromone, trail asymmetry has a significant effect on trail choice. Ants preferentially follow the branch deviating least from straight, and this effect increases as asymmetry increases (47% at 0°, 54% at 30°, 57% at 45°, 66% at 60° and 73% at 90°). However, when pheromone is only present on one branch, the graded effect of asymmetry disappears. Overall, however, there is an effect of asymmetry as the preference of ants for the pheromone‐marked branch over the unmarked branch is reduced from 65%, when it is the less deviating branch, to 53%, when it is the more deviating branch. These results demonstrate that trail asymmetry influences ant decision‐making at bifurcations and that this information interacts with trail pheromone presence in a non‐hierarchical manner.     

Larval feeding behaviour of Tetanocera elata (Diptera: Sciomyzidae): potential biocontrol agent of pestiferous slugs

Examining predatory behaviour is useful for determining the potential of novel biocontrol agents. We investigated the predatory behaviour of Tetanocera elata (Fabricius) larvae on the pestiferous slug Deroceras reticulatum (Müller). Results indicate three prey-finding strategies, including the predator reaching its prey without previous contact with it or its mucus trail.     

Foraging in highly dynamic environments: leaf‐cutting ants adjust foraging trail networks to pioneer plant availability

Major shifts in the availability of palatable plant resources are of key relevance to the ecology of leaf‐cutting ants in human‐modified landscapes. However, our knowledge is still limited regarding the ability of these ants to adjust their foraging strategy to dynamic environments. Here, we examine a set of forest stand attributes acting as modulating forces for the spatiotemporal architecture of foraging trail networks developed by Atta cephalotes L. (Hymenoptera: Formicidae: Attini). During a 12‐month period, we mapped the foraging systems of 12 colonies located in Atlantic forest patches with differing size, regeneration age, and abundance of pioneer plants, and examined the variation in five trail system attributes (number of trails, branching points, leaf sources, linear foraging distance, and trail complexity) in response to these patch‐related variables. Both the month‐to‐month differences (depicted in annual trail maps) and the steadily accumulating number of trails, trail‐branching points, leaf sources, and linear foraging distance illustrated the dynamic nature of spatial foraging and trail complexity. Most measures of trail architecture correlated positively with the number of pioneer trees across the secondary forest patches, but no effects from patch age and size were observed (except for number of leaf sources). Trail system complexity (measured as fractal dimension; Df index) varied from 1.114 to 1.277 along the 12 months through which ant foraging was monitored, with a marginal trend to increase with the abundance of pioneer stems. Our results suggest that some leaf‐cutting ant species are able to generate highly flexible trail networks (via fine‐tuned adjustment of foraging patterns), allowing them to profit from the continuous emergence/recruitment of palatable resources.     

The Fish Trail Undichna quadrisulcata isp. nov. from the Eocene of Spitsbergen

Abstract

Undichna quadrisulcata isp. nov. is described from the Eocene of Spitsbergen, where it occurs together with xiphosuran (horseshoe crabs) traces in upper shoreface to foreshore deltaic sandstone. This is the first record of a marine (deltaic) Undichna from the Eocene. The trail consists of two or three pairs of paralleling sinusoidal grooves (in epirelief) or ridges (in hyporelief). Previous records of this trace fossil from the Carboniferous and Permian were assigned to U. insolentia Anderson, 1976 Anderson, A. M. 1976. Fish trails from the early Permian of South Africa. Palaeontology 19(2): 397–409. [Google Scholar], which, however, comprises a more complex pattern. The repeated occurrence of U. quadrisulcata isp. nov. in the Carboniferous, Permian, Triassic and Eocene, independent from U. insolentia, justifies its own ichnospecies name and suggests a different kind of producer. U. quadrisulcata isp. nov. is interpreted as a fish trail, probably produced by a representative of Amiiformes (actinopterygian, ray-finned fish) or coelacanth fish.     

Recruitment Behavior in the Ant Genus Polyrhachis (Hymenoptera, Formicidae)

We present a detailed behavioral analysis of the signals involved in recruitment of 11 syntopic Polyrhachis species from West Malaysia. We found a considerable variety of recruitment techniques, including social carrying behavior, tandem running, group recruitment, and a technique which we call leader-independent trail communication. The latter mode superficially resembles chemical mass communication (sensu Wilson, 1962). All these recruitment techniques involve mechanical invitation behavior inside the nest, comprising back-and-forth jerking or pulling movement often combined with a sideways waggling. However, not in all cases of leader-independent trail communication is a mechanical invitation behavior obligatory. The trail pheromone of all investigated Polyrhachis species originates from the hindgut. Only in the tandem running P. proxima do additional secretions from the poison gland appear to be involved in tandem calling.     

Crowding increases foraging efficiency in the leaf-cutting ant <Emphasis Type="Italic">Atta colombica</Emphasis>

Many animals, including humans, organize their foraging activity along well-defined trails. Because trails are cleared of obstacles, they minimize energy expenditure and allow fast travel. In social insects such as ants, trails might also promote social contacts and allow the exchange of information between workers about the characteristics of the food. When the trail traffic is heavy, however, traffic congestion occurs and the benefits of increased social contacts for the colony can be offset by a decrease of the locomotory rate of individuals. Using a small laboratory colony of the leaf-cutting ant Atta colombica cutting a mix of leaves and Parafilm, we compared how foraging changed when the width of the bridge between the nest and their foraging area changed. We found that the rate of ants crossing a 5 cm wide bridge was more than twice as great as the rate crossing a 0.5 cm bridge, but the rate of foragers returning with loads was less than half as great. Thus, with the wide bridge, the ants had about six times lower efficiency (loads returned per forager crossing the bridge). We conclude that crowding actually increased foraging efficiency, possibly because of increased communication between laden foragers returning to the nest and out-going ants. Received 15 December 2006; revised 16 February 2007; accepted 19 February 2007.