Perri K. Eason

New birds on the block: new neighbors increase defensive costs for territorial male willow ptarmigan

Previous researchers have hypothesized that site-faithful animals may benefit from the presence of familiar neighbors. This study compares the relative costs of territorial defense against new and former neighbors by male willow ptarmigan (Lagopus lagopus). Territorial defense against new neighbors appeared to require a greater expenditure of both time and effort than did defense against former neighbors. Territorial males that had several new neighbors spent a higher proportion of time fighting than did males with fewer new neighbors, and males with both new and former neighbors spent a greater amount of time fighting with their new neighbors, on average, than with their former neighbors. In addition, fights with new neighbors occurred relatively more frequently and were longer than fights with former neighbors. Finally, fights involving new neighbors tended to escalate to higher levels than fights between former neighbors. Reduced defensive costs for site-faithful, territorial males may provide one explanation for the tendency of males to be more site-faithful than females in many species.

The use of landmarks to define territorial boundaries.

Numerous anecdotal reports suggest that members of many territorial species use naturally occurring landmarks to define the boundaries of their territories. In the work reported here, we first tested whether artificial landmarks would be adopted as boundaries by territorial male cicada killer wasps, Sphecius speciosus. To perform this test, we set out wooden dowels on a flat, grassy lawn on which male wasps were defending mating territories. The dowels were situated so that they did not coincide with any existing territorial boundary. After we provided the dowels, the wasps established new territorial boundaries coinciding with the dowels. We hypothesized that using visual landmarks as territorial borders might lower defensive costs, and indeed, focal samples on territorial wasps revealed that borders that were defined by dowels cost less to defend than did borders that were not defined by any landmark. This result suggests that the use of natural landmarks as territorial boundaries may have evolved as a result of the reduced defensive costs that accrue to these boundaries. Furthermore, defensive costs may not depend directly on territory size: territory owners may be able to reduce defensive costs by selecting sites with high tactical defensibility. Copyright 1999 The Association for the Study of Animal Behaviour.

Relationships between spacing behavior and growth rates: a field study of lizard feeding territories

SummaryRelationships between spacing behavior and growth rates were investigated in a field experiment with juvenile lizards, Anolis aeneus. The behavioral variable most closely related to juvenile growth was distance moved per unit time. This variable had a curvilinear relationship with growth, such that juveniles moving approximately 400 cm/h grew more rapidly than those traveling either larger or shorter distances per unit time. Daily fluctuations in arthropod abundance were also related to growth rates, with restricted growth during periods of low food availability. Temporal fluctuations in prey and distance traveled per unit time had independent effects on growth; together these two variables accounted for 43% of the variance in growth rate for the juveniles in this study.Territory size, overlap and social status appeared to affect growth indirectly, by influencing distance traveled per unit time. Optimal travel distances of around 400 cm/h were most likely when a juvenile had a relatively exclusive territory of about 0.5 m2. High ranking juveniles were more apt to achieve this spacing pattern than were low ranking juveniles, but some high ranking juveniles had very large territories, extensive overlap with subordinates, supraoptimal travel distances and relatively low growth rates. Low ranking juveniles tended to fall into two groups: subordinates, with a small home range overlapping that of a more dominant individual and low travel distances, and floaters, with a large home range overlapping several more dominant individuals and high travel distances. Although a few low ranking juveniles achieved travel distances permitting high growth rates, most had either supra or suboptimal travel distances and relatively low growth rates.

SIZE DETERMINANTS IN TERRITORIES WITH INFLEXIBLE BOUNDARIES: MANIPULATION EXPERIMENTS ON WHITE‐WINGED TRUMPETERS’ TERRITORIES

We investigated determinants of territory size in White-winged Trumpeters (Psophia leucoptera), frugivorous, cooperatively breeding birds that defend large, per- manent, all-purpose territories in lowland Amazonian rain forest. During a 7-mo period, we measured changes in food density at a site in Manu National Park, Peru, and conducted full-day focal samples on individuals that allowed us to record daily food intake of territorial birds. We used data from laboratory analyses on energy content of fruit species eaten by trumpeters to calculate a phenology of energy content for food available on territories of focal groups, and to calculate daily energy intake of focal trumpeters. Additionally, we used lab measurements of basal metabolic rate of trumpeters to estimate daily energy requirements of wild trumpeters. Both census and focal sample data suggested that food availability on trumpeter ter- ritories varied widely, sometimes greatly exceeding and sometimes falling short of the amount that we calculated was necessary to meet average daily energy requirements of groups. To determine whether trumpeter territory size was related to food density, we conducted fruit removals. Every day, we removed an amount of fruit from the territory that was equivalent to the amount of fruit ingested daily by the focal group during a control period preceding the removal experiment. We conducted removal experiments during pe- riods when food density on territories appeared to be abundant and also when food abun- dance appeared to be low. Trumpeter food consumption did not change when fruit was removed during periods of resource abundance; however, when experimental removals were conducted during periods of food scarcity, the total energy value of food consumed de- creased significantly. These results suggest that food abundance on trumpeter territories sometimes exceeds and sometimes is close to or below the amount needed to meet energy needs of the groups. Based on our data, we propose that territory size of White-winged Trumpeter groups reflects some minimum size needed to provide the group with a baseline level of food intake during seasonal periods of decreased food abundance.

Effects of landmarks on territorial establishment

Abstract The period of territorial settlement is critical for territorial species, and the initial disputes to fix the boundaries can be energetically expensive. Territorial residents may be able to reduce defensive costs during settlement by selecting territories with landmarks at the sites of potential boundaries. We examined the effects of landmarks on defensive costs in a laboratory study of a cichlid fish, the blockhead, Steatocranus casuarius . In the landmark treatment, we placed a row of flat rocks across the centre of the aquaria; trials in the control treatment were identical but lacked landmarks. When landmarks were present, blockheads spent significantly less time in territorial defence, as they had fewer and shorter aggressive interactions with their neighbours. In addition, fights in landmark trials tended to be of lower intensity than fights in control trials: most fights in landmark trials included only low-level displays but most fights in control trials included physical contact. Both of these measures thus indicated that defensive costs were lowered by landmarks. In addition, in landmark trials typically both pairs of fish successfully established territories; in contrast, in control trials generally only one pair was able to establish a territory, with the other pair being evicted. The presence of landmarks appeared to make possible the division of the area available for settlement, with pairs establishing smaller territories than when there were no landmarks. Copyright 2003 Published by Elsevier Science Ltd on behalf of The Association for the Study of Animal Behaviour.

Effects of Vegetation Loss on a Sand Dune Lizard

Habitat degradation in the form of vegetation loss often decreases the abundance of various species of reptiles (Fleischner 1994, Smith et al. 1996). Several reasons have been proposed for why vegetation loss should decrease abundance, including reduction of thermoregulatory patches, decreased prey availability, and increased predation from being in more exposed areas (Jones 1981, Norbury 2001). Vegetation loss could adversely affect lizards because they might be unable to escape lethal substrate temperatures (Adolph 1990, Carrascal et al. 1992). Vegetation loss may also decrease food availability, which could affect reptile abundance either directly or indirectly by affecting behavior. Individuals might compensate for reduced food availability by moving farther in search of prey or spending more time foraging, which might increase their susceptibility to predators (MacArthur and Pianka 1966, Hinsley 2000). Vegetation loss might additionally increase predation risk because fewer refuges are available. We examined the effects of vegetation loss by livestock grazing and agricultural practices on the abundance of the lizard Acanthodactylus longipes. To investigate the differences in abundance we found, we next compared body condition, thermoregulatory behavior, and activity patterns of lizards from unprotected and protected habitats. To test the hypothesis that vegetation loss affected thermoregulatory behavior, we compared the time that A. longipes spent thermoregulating by postural changes in unprotected and protected habitats. We expected that lizards in habitats with less vegetation might spend more time thermoregulating at higher temperatures by postural changes, while lizards in protected habitats might use vegetation more frequently. To test whether vegetation loss affected food availability or susceptibility to predation, we examined whether lizards in habitats experiencing vegetation loss moved greater distances or spent more time moving than in protected habitats. We assumed that if food availability were decreased, lizards would compensate by moving greater distances while foraging or spending more time foraging. This analysis also assumes that more active lizards are at higher risk of predation due to greater visibility. To provide an additional assessment of predation risk, we examined the distance from vegetation at which the lizard was observed. A. longipes is a common diurnal lizard that inhabits the sand dune deserts of North Africa and the Middle East; it thermoregulates by postural changes and by using vegetation (Attum 2004). A. longipes is ecologically and morphologically specialized for psammophile environments (Arnold 1981, Baha El Din 2001).

Colour bands, combs and coverable badges in willow ptarmigan

Willow ptarmigan, Lagopus lagopus, possess red supra-orbital combs. If this secondary sexual structure is important in attracting mates or in male-male competition, then colour banding males with red or orange bands (RO) could influence their pairing and reproductive success, survival and the amount of aggression directed towards them. Males with RO bands did not have more mates than those without RO bands, nor did males unbanded in year x improve their pairing success in year x + 1 when they were given RO bands. In a female removal experiment, males with RO bands did not have more females settling on their territories than males with other band colours. Number of chicks fledged from successful nests and annual survival did not differ for RO and non-RO males. Monogamous and polygynous males had similar comb areas which were larger than the combs of unmated males. When pairing statys was controlled, comb area was not related to annual survival or number of chicks fledged. Males with RO bands did not have larger combs than non-RO males. Area of comb was correlated with territory size in years of high breeding density, but not in years of low breeding density. Radiotagged non-territorial males did not preferentially intrude upon the territories of males with RO bands and song rates, number of border disputes, mean length of border disputes, and territorial intrusion rates did not differ significantly for RO and non-RO males. These results suggest that colour-banding willow ptarmigan with red colour bands does not have a negative or positive effect on reproductive success or survival, and thus the data do not support the coverable badge hypothesis.

Proximate Constraints on Intruder Detection in the Dragonfly Perithemis tenera (Odonata: Libellulidae): Effects of Angle of Approach and Background

Abstract The implications of insects’ vision for territorial defense have been relatively little studied in the field. In the dragonfly Perithemis tenera Say we investigated whether either the angle at which an intruder was viewed by a territorial resident or the background against which it was viewed affected the detection of that intruder. Residents detected intruders at a greater distance if the intruders were directly in front of them; they also detected more intruders in front of them than from other angles. Intruders viewed against distant vegetation were detected more readily than were intruders against near vegetation. Residents detected more intruders viewed against distant vegetation than viewed against near vegetation; however, more intruders than expected were detected against near vegetation. The probability of detecting intruders depends on the angle at which they are viewed and the background behind them. Hence, there may be selection on territorial residents to adjust their orientation and space use to enhance their view of their territory and intruders.

THE EFFECT OF VISIBILITY ON SPACE USE BY TERRITORIAL RED-CAPPED CARDINALS

One of the factors that may influence an animals use of space is visibility, which in territorial species can determine how readily an individual can monitor its territory for conspecific intruders. We hypothesized that territorial red-capped cardinals (Paroaria gularis) would prefer locations that provided them with good views of their territories. Red-capped cardinals defend territories along lakes and rivers in the Amazon Basin, and visibility can vary widely within these territories. We defined visibility as the percentage of a territory that could be seen from a particular location. Visibility was measured by dividing each territory into 20 m segments and calculating the proportion of the territory that was visible from each segment. Cardinals did not distribute their time evenly within their territories: focal observations revealed that cardinals spent more time in the segments of their territory that afforded them the best view of their territory. This preference is unlikely to be due to differences in food availability, as the abundance of arthropod prey did not vary between high-visibility sites (peninsulas) and low-visibility sites (bays). Cardinals probably benefited from their disproportionate use of sites with high visibility because conspecific intruders were more likely to be detected from those sites.

Camera Trap Observations of Nonhabituated Critically Endangered Wild Blonde Capuchins, Sapajus flavius (Formerly Cebus flavius)

Habituation presents major challenges for the study of wild primates, particularly in areas where threats such as hunting pressure and increasing forest fragmentation exist. This study describes the use of ground camera trapping to investigate nonhabituated blonde capuchins. Capuchins are arboreal animals, but often use the ground when foraging. Thus, we hypothesized that a ground-baited camera trapping station would be an efficient method to document the presence of capuchins, and to collect information about aspects of their social behavior and ecology. We conducted 92 systematic trapping days over 15 months (from December 2010 to February 2011 and from August 2011 to July 2012). The capuchins visited the trapping stations 43 times. All visits occurred between 05:13h and 17:32h, and lasted 3 min-2:03 h. Sixty-five percent of the photographs included our target species. Groups contained up to 46 individuals and were multimale-multifemale. We recorded no monkeys at the trapping stations during August and November (2011) and January (2012). Infants were more likely to be carried than not. Infants were carried by both sexes; however, 96% of photographs showed females as carriers. Adult males always arrived first at the camera trapping stations, suggesting that males led the group’s movements. The ground-baited camera trapping stations proved effective for confirming the presence of the blonde capuchins in the study site and for documenting aspects of their social behavior. The technique could potentially be used to provide comparative data among populations of this and other primate species in areas where habituation is difficult or risky to the primates.