Thermoregulation in male western cicada killers (Sphecius grandis Say) in the Chihuahuan desert

(1) Male western cicada killers (Sphecius grandis) had elevated, apparently regulated, thorax temperatures during territorial patrolling. (2) Abdomen temperature increased steeply with increasing ambient temperature, approaching thorax temperature when ambient temperature exceeded 35 °C. (3) Both indirect evidence and heating experiments demonstrated the apparent ability to shunt heat from thorax to abdomen. (4) Dead, dry wasps reached lethal temperatures when placed in full sunlight on the bare ground, and substantially lower temperatures on plants. (5) The percentage of males perching was extremely low, occurring primarily during early morning hours. Most perching occurred on plants, and very little on the ground. (6) In contrast to what has been reported for eastern cicada killers (Sphecius speciosus), S. grandis males did not appear to use sophisticated behaviors to regulate body temperature during territorial defense, relying primarily on physiological mechanisms. (7) This strategy may be more appropriate for S. grandis in the hotter, drier environment of the lowland Chihuahuan desert.     

The reproductive period of tarantulas is constrained by their thermal preferences (Araneae,Theraphosidae)

Locomotor and physiological performance of ectotherms are affected by temperature. Thermoregulation is achieved by changes in behavior and the selection of micro-habitats with adequate temperatures to maintain the body temperature (T_b) within a range of preference. Apart from this temperature dependence at spatial scales, ectotherms are also affected by temperature at temporal scale. For instance, ectotherms can only be active some months of the year, particularly in temperate environments. Tarantulas are ectotherms that live in burrows most of their life. Nevertheless, after the sexual maturation molt, males leave their refugia and start a wandering life searching for females to mate. The reproductive period varies among species. In some species walking males are seen in late spring or early summer, while in other species males are only seen during fall or winter. Apart from the differences in lifestyles after maturation, tarantulas exhibit sexual dimorphisms in longevity and body mass, having smaller, shorter-lived males. Thus, to optimize energetic budgets, decreasing thermoregulation costs, we hypothesize and examine a putative correlation between an individual's preferred body temperature (T_pref) and the environmental temperature during the reproductive period. Hence, we characterize T_pref in seven tarantula species and analyze which factors (i.e., time of day, body mass, and sex) correlated with it. Furthermore, we assess putative correlated evolution of T_pref with ambient temperature (minima, mean, and maxima) during the reproductive period by means of phylogenetic independent contrasts. We did not find differences in thermal preferences between sexes; and only one species, Acanthoscurria suina, exhibited diel differences in T_pref. We found evidence of correlated evolution between T_pref and minimum temperature during the reproductive period among all seven species studied herein. Our results show that the reproductive period is constrained by thermal preferences, dictating when males can start their wandering life to mate.     

Stridulatory Sound-Production and Its Function in Females of the Cicada Subpsaltria yangi

Acoustic behavior plays a crucial role in many aspects of cicada biology, such as reproduction and intrasexual competition. Although female sound production has been reported in some cicada species, acoustic behavior of female cicadas has received little attention. In cicada Subpsaltria yangi, the females possess a pair of unusually well-developed stridulatory organs. Here, sound production and its function in females of this remarkable cicada species were investigated. We revealed that the females could produce sounds by stridulatory mechanism during pair formation, and the sounds were able to elicit both acoustic and phonotactic responses from males. In addition, the forewings would strike the body during performing stridulatory sound-producing movements, which generated impact sounds. Acoustic playback experiments indicated that the impact sounds played no role in the behavioral context of pair formation. This study provides the first experimental evidence that females of a cicada species can generate sounds by stridulatory mechanism. We anticipate that our results will promote acoustic studies on females of other cicada species which also possess stridulatory system.     

Sexual selection and the physiological consequences of habitat choice by a fiddler crab

In mid-Atlantic salt marshes, reproductively active male sand fiddler crabs, Uca pugilator, use a single greatly enlarged major claw as both a weapon to defend specialized breeding burrows from other males and an ornament to attract females for mating. During the summer breeding season, females strongly prefer to mate with males controlling burrows in open areas high on the shore. Food availability decreases while temperature and desiccation stress increase with increasing shore height, suggesting that the timing and location of fiddler crab mating activity may result in a potential trade-off between reproductive success and physiological condition for male crabs. We compared thermal preferences in laboratory choice experiments to body temperatures of models and living crabs in the field and found that from the perspective of a fiddler crab, the thermal environment of the mating area is quite harsh relative to other marsh microhabitats. High temperatures significantly constrained fiddler crab activity on the marsh surface, a disadvantage heightened by strongly reduced food availability in the breeding area. Nevertheless, when the chance of successfully acquiring a mate was high, males accepted a higher body temperature (and concomitantly higher metabolic and water loss rates) than when the chances of mating were low. Likewise, experimentally lowering costs by adding food and reducing thermal stress in situ increased fiddler crab waving display levels significantly. Our data suggest that fiddler crabs can mitigate potential life history trade-offs by tuning their behavior in response to the magnitude of both energetic and non-energetic costs and benefits.     

Thermal relations of dwarf caiman, Paleosuchus palpebrosus, in a hillside stream: Evidence for an unusual thermal niche among crocodilians

Body temperatures of 13 Paleosuchus palpebrosus, 7 males and 6 females, were monitored by radio-telemetry during cold periods (dry season) and warm periods (wet and dry seasons) in a stream draining into the Brazilian Pantanal. The mass of the caimans varied from 2.5 to 20.0 kg, and snout–vent length from 47.5 to 95.0 cm. Mean monthly body temperature was 21.6 °C, and varied from 20.1 to 25.6 °C throughout the year. Body temperature was correlated with air and water temperature but did not differ between males and females. Unlike all other crocodilians investigated in detail to date, the caimans did not show evidence of attempts to obtain higher body temperatures when ambient temperatures were low, and had low and generally constant temperatures in relation to the surrounding air and water throughout the year. The caimans remained in burrows during cold periods in the dry season, which may explain why they did not seek higher temperatures. Tolerance of relatively low and constant body temperatures may be a key adaptation of species of Paleosuchus, allowing them to occupy environments inhospitable to other crocodilians.     

Territorial Pheromones of Female Red-backed Salamanders

Pheromones provide an important source of communication during social interactions of caudate amphibians. To further examine their use in territorial defense, we performed a laboratory experiment to test the hypothesis that non-courting female red-backed salamanders (Plethodon cinereus) deposit pheromones in or on fecal pellets, as males are known to do during territorial advertisement. Four conditions were tested: (1) a burrow marked with a female's own pellet vs. a burrow marked by a conspecific female's pellet, (2) own vs. unmarked burrows, (3) conspecific vs. unmarked burrows, and (4) paired unmarked burrows as a control. Females nose-tapped (for olfactory cues) their own and conspecific pellets about equally. However, they spent significantly more time in both threat and submissive behavior toward the conspecific pellets and spent significantly more time in their own marked burrows. We infer that female P. cinereus do deposit pheromones in or on fecal pellets and that these pellets may be used to advertise territories. The behavioral responses of females toward pellets of other females were more aggressive than those of males (in a previous study) toward pellets of other males.     

Thermal biology, torpor use and activity patterns of a small diurnal marsupial from a tropical desert: sexual differences

Many small desert dasyurids employ torpor almost daily during winter, because cold nights and low food availability impose high energetic costs. However, in Western Australia the arid zone extends into tropical, coastal regions, where winter temperature conditions are far less severe. We studied the thermal biology and activity patterns of free-ranging kaluta (~27 g), a dasyurid restricted to these tropical spinifex deserts, during the Austral winter (June–July) and in addition quantified activity patterns in captivity. Unlike most dasyurids, wild and captive kalutas were almost exclusively diurnal and retreated into underground burrows during the night. Despite being active during the warmer part of the day, kalutas entered torpor daily. However, torpor patterns differed remarkably between males and females. While females spent most of the night torpid at body temperatures (T _b) as low as 21°C, close to soil temperature, males entered multiple short and shallow bouts (T _b > 25°C) during the night. Males also maintained higher T _bs during the early morning when active, occupied larger home ranges and covered greater distances while foraging than females. Hence, males appear to expend more energy than the similar-sized females both while foraging and during the rest phase. We propose that physiological as well as behavioural preparations for the September mating season that culminate in a complete male die-off might already impose energetic costs on males during winter.     

The Sun,Moon, Wind,and Biological Imperative–Shaping Contrasting Wintertime Migration and Foraging Strategies of Adult Male and Female Northern Fur Seals (Callorhinus ursinus)

Adult male and female northern fur seals (Callorhinus ursinus) are sexually segregated in different regions of the North Pacific Ocean and Bering Sea during their winter migration. Explanations for this involve interplay between physiology, predator-prey dynamics, and ecosystem characteristics, however possible mechanisms lack empirical support. To investigate factors influencing the winter ecology of both sexes, we deployed five satellite-linked conductivity, temperature, and depth data loggers on adult males, and six satellite-linked depth data loggers and four satellite transmitters on adult females from St. Paul Island (Bering Sea, Alaska, USA) in October 2009. Males and females migrated to different regions of the North Pacific Ocean: males wintered in the Bering Sea and northern North Pacific Ocean, while females migrated to the Gulf of Alaska and California Current. Horizontal and vertical movement behaviors of both sexes were influenced by wind speed, season, light (sun and moon), and the ecosystem they occupied, although the expression of the behaviors differed between sexes. Male dive depths were aligned with the depth of the mixed layer during daylight periods and we suspect this was the case for females upon their arrival to the California Current. We suggest that females, because of their smaller size and physiological limitations, must avoid severe winters typical of the northern North Pacific Ocean and Bering Sea and migrate long distances to areas of more benign environmental conditions and where prey is shallower and more accessible. In contrast, males can better tolerate often extreme winter ocean conditions and exploit prey at depth because of their greater size and physiological capabilities. We believe these contrasting winter behaviors 1) are a consequence of evolutionary selection for large size in males, important to the acquisition and defense of territories against rivals during the breeding season, and 2) ease environmental/physiological constraints imposed on smaller females.     

Thermoregulation in the cicada Platypedia putnami variety lutea (Homoptera: Tibicinidae) with a test of a crepitation hypothesis

• 1.Measurements of body temperature (T_b) in the field demonstrate that Platypedia putnami var. lutea Davis regulates T_b through behavioral mechanisms.
• 2.Thermal responses (minimum flight temperature 17.3°C, maximum voluntary tolerance-temperature 32.5°C, and heat torpor temperature 44.4°C) of P. putnami var. lutea are related to the altitude of their habitat.
• 3.Water loss rates increase with ambient temperature (T_a). Water loss rates are not significantly different at the extremes of the active T_b range but increase significantly when exposed to elevated T_a.
• 4.Acoustic activity was restricted at 6.7°C T_b range. This is similar to the lower end of the T_b range for singing measured in cicada species that produce sound with a timbal mechanism.
• 5.The use of the wing musculature to produce acoustic signals in P. putnami var. lutea does not increase the T_b range over which the species can call compared to timbal calls produced by other cicada species.

     

Thermal biology, torpor, and activity in free-living mulgaras in arid zone Australia during the winter reproductive season

Little is known about the energy conservation strategies of free-ranging marsupials living in resource-poor Australian deserts. We studied activity patterns and torpor of free-living mulgaras (Dasycercus blythi) in arid central Australia during the winter of 2006. Mulgaras are small (approximately 75 g), nocturnal, insectivorous marsupials, with a patchy distribution in hummock grasslands. Mulgaras (six males, three females) were implanted intraperitoneally with temperature-sensitive transmitters and monitored for 6-55 d. Temperature profiles for different microhabitats and the thermal properties of soil and a number of burrows were also measured. Air temperature ranged from -3 degrees C at night to 30 degrees C during the day. Although burrows buffered temperature extremes, the thermal diffusivity of the sandy soil was high, and many burrows were shallow. Hence, soil and burrow temperatures averaged about 15 degrees C. The activity of mulgaras was often restricted to a few hours after sunset, before they retired into their burrows. Mulgaras employed torpor frequently, often entering torpor during the night and arousing around midday, with arousals occurring later on cooler days. Shallow burrows allowed cooling below mean T(soil). Consequently, body temperatures as low as 10.8 degrees C were observed. The longest torpor bout was 20.8 h. Torpor patterns changed seasonally and differed between males and females. From June to August, females entered torpor almost daily despite mating and gestation, but from the end of the gestation period onward, they remained normothermic. In contrast, males showed only shallow and short torpor during the mating season, but from mid-July, a transition to more frequent and deeper torpor resembling that of females was observed. Apparently, in both sexes, the reproductive effort entails energetic costs, but torpor, as an energy-saving mechanism, and reproduction are not exclusive in mulgaras. In a resource-poor environment during the least productive part of the year, frequent torpor seems to provide the means to compensate for the increased energetic costs associated with reproduction.     

How temperature,humidity, and burrow selection affect evaporative water loss in desert tortoises

By combining field behavior and microclimate measurements with biophysical models, I assessed the value of underground burrows as thermal refuge for desert tortoises (Gopherus agassizii) and their additional advantage for water conservation. Between 1000–1200 h, humidity was significantly higher and temperature and predicted evaporative water loss (EWL) lower inside burrows than on the surface. Greater burrow length and smaller entrances were correlated with greater burrow humidity. Furthermore, the range of variation in humidity, temperature and EWL over 24 h was greater on the surface than inside burrows. Thus, surface conditions would be more favorable during certain times of day.     

Salamander territoriality: pheromonal markers as advertisement by males

A laboratory experiment was performed to test the hypothesis that male red-backed salamanders (Plethodon cinereus) use pheromones contained in faecal pellets to identify male-marked territories. Each of 25 males was tested randomly under four conditions: (1) a burrow marked with its own faecal pellet versus one marked with a conspecific's pellet; (2) own-marked versus surrogate-marked burrows (the surrogate being a pellet of wadded paper); (3) conspecific-marked versus surrogate-marked burrows; and (4) a control of two surrogate-marked burrows. Males spent significantly more time in own-marked than in conspecific-marked burrows and significantly more time in surrogate-marked than in conspecific-marked burrows. Males favoured own-marked over surrogate-marked burrows. No position bias was found in the control. Males spent significantly more time nose-tapping (olfactory sampling) to a conspecific's pellet when it was paired with a surrogate but showed no differences in the other three tests. Significantly more time was spent in a submissive posture in front of the conspecific-marked burrow than in front of either their own-marked or the surrogate-marked burrows; no difference was found between own-marked versus surrogate-marked burrows or in the control. Time spent in the threat posture did not differ significantly between burrows in any condition. These data permit the inferences that males of P. cinereus use faecal pellets to mark and identify territories, avoid or display submissively toward burrows marked by conspecific males, and prefer own-marked shelters.     

Take-off performance under optimal and suboptimal thermal conditions in the butterfly <Emphasis Type="Italic">Pararge aegeria</Emphasis>

Realized fitness in a fluctuating environment depends on the capacity of an ectothermic organism to function at different temperatures. Flying heliotherms like butterflies use flight for almost all activities like mate location, foraging and host plant searching and oviposition. Several studies tested the importance of ambient temperature, thermoregulation and butterfly activity. Here, we test the influence of variation in flight morphology in interaction with differences in body temperature on locomotor performance, which has not been thoroughly examined so far. Take-off free flight performance was tested at two different body temperatures in males and females of the speckled wood butterfly Pararge aegeria. We found that both males and females accelerated faster at the optimal body temperature compared to the suboptimal one. The multivariate analyses showed significant sex-specific contributions of flight morphology, body temperature treatment and feeding load to explain variation in acceleration performance. Female and male butterflies with a large relative thorax (i.e. flight muscle investment) mass and large, slender wings (i.e. aspect ratio) accelerated fast at optimal temperature. However, high aspect ratio individuals accelerated slowly at suboptimal temperature. Females of low body mass accelerated fast at optimal, but slowly at suboptimal body temperature. In males, there was an interaction effect between body and relative thorax mass: light males with high relative thorax mass had higher performance than males with a low relative thorax mass. In addition, relative distance to the centre of forewing area was positively related to acceleration at both temperatures in males. Males and females with higher feeding loads had lower levels of acceleration. Finally, males that were able to accelerate fast under both temperatures, had a highly significantly heavier relative thorax, lower body and abdomen mass. More generally, this study shows that the significance of butterfly flight morphology in terms of flight performance is at least partially dependent on body temperature.     

Inter-male competition and mating success in the field cricket,Gryllus bimaculatus (de Geer)

Males of the field cricket Gryllus bimaculatus compete aggressively for the acquisition of burrows and females. The effect of population density on the nature of encounters between males, and factors affecting individual competitive ability were examined. Aggression was reduced in high population densities, both in terms of the proportion of encounters leading to aggression and in the intensity of aggressive disputes. The addition of burrows and females increased aggressiveness and removed population density effects. Individual competitive ability was determined primarily by body size and secondly, by an individual's past experience of winning (‘confidence’). Competitive ability, prior residence in burrows and the presence of females all appear to influence the outcome of aggressive disputes. Variation in calling frequency of males was influenced both by population density and competitive ability; males who called more often had a greater encounter rate with females. Females were more likely to mate with burrow residents. However, amongst residents, larger males gained more matings. The potential for female choice in this species is discussed.     

Pillar Function in the Fiddler Crab Uca beebei (II): Competitive Courtship Signaling

Male Uca beebei court and attract females into burrows they defend on muddy sand flats in the intertidal zone on the Pacific coast of the tropical Americas. Mating, oviposition and incubation (breeding) occur underground in males' burrows. Some courting males build mud pillars (2 cm high) at the entrance of their burrow. The purpose of this field study was to assess the role of pillars in competitive courtship signaling among males. I studied the effect of pillars on female behavior by recording the responses of wandering females to courtship from males resident at burrows with and without pillars. I also caught females, released them individually in a circular arena with an equal number of empty burrows with and without pillars around its circumference, and chased the females with a simulated avian predator. Females moved to burrows of both types more often when they were courted (82%) than when they were chased (67%). Receptive females were attracted to the burrows of the males that courted them significantly more often (97%) when these burrows had pillars than when they lacked pillars (66%). However, once females entered males' burrows they were equally likely to remain, mate and breed in both types of burrows. Females also more often moved to burrows with pillars (66%) than to burrows without pillars when they ran from the simulated predator. Both male courtship displays and pillars probably provide cues females use to locate males' burrows. The visual similarity between pillars and a display courting males give immediately before they enter their burrows suggests that pillars are icons of the display. The effect of pillars on female behavior, the timing of pillar building relative to when females choose mates, and contrasts in the behavior of males that do and those that do not build pillars suggest that pillar building has evolved due to competition among males to attract females into their burrows.     

Sex, size and colour in a semi-terrestrial crab, Heloecius cordiformis (H. Milne Edwards, 1837)

We investigated the relationship between sex, size and colour in the little studied Australian endemic semaphore crab, Heloecius cordiformis, and related it to the crabs' social system with the aim of identifying the potential signalling function of claw colour.Equal sampling of crabs from all size classes revealed a strong relationship between sex, size and claw colour. Purple-clawed males were larger and had larger claws than pink-, orange- or green-clawed males. Male claws showed positive allometric growth: relative to body size, purple-clawed males had larger claws. The largest females had pink claws; the few with purple claws were no larger than immature green-clawed crabs. Female claws grow isometrically with the body so the relative claw size did not differ among the female colour classes. Quantitative measurements of claw colour revealed spectral differences between these subjectively described colours. The purple claws typical of large males also contrasted more strongly against the mudflat background than the other colours.Heloecius copulate outside female-owned burrows and probably within male-owned burrows. The male's waving display, in which both claws are raised and lowered, may feature in both mating strategies: as a territorial display and to attract wandering females. Large males are competitively superior so size, and potentially colour, are important in territorial disputes and may also feature in mate choice.     

Acute corticosterone elevation enhances antipredator behaviors in male tree lizard morphs

In response to stressful events, most vertebrates rapidly elevate plasma glucocorticoid levels. Corticosterone release stimulates physiological and behavioral responses that can promote survival while suppressing behaviors that are not crucial to immediate survival. Corticosterone also has preparatory effects for subsequent stressors. Using male tree lizards (Urosaurus ornatus), we tested our prediction that elevated corticosterone is important for mediating and enhancing antipredator behaviors. Male tree lizards express developmentally fixed polymorphisms that are mediated by early organizational actions of steroid hormones, and thus we also tested the hypothesis that morph-specific differences in antipredator behaviors of adults are independent of circulating corticosterone levels. Plasma corticosterone levels were elevated exogenously for 12-16 h using non-invasive dermal patches, and we then compared the behavioral responses of these corticosterone-patched males to control-patched males during a simulated encounter with a caged predator (collared lizard, Crotaphytus nebrius) in outdoor enclosures. Elevating corticosterone did not alter the antipredator behavioral repertoire of each male morph, but did enhance their responses during the predator encounter: all corticosterone-patched males responded more quickly, hid longer, and displayed more toward the predator than control-patched males. With the corticosterone patch, the non-territorial and wary orange morph was still behaviorally the most wary morph, responding more quickly and hiding longer than either the bolder orange-blue or mottled morphs. Smaller males were generally warier than larger males, regardless of the endocrine treatment or color morph type. In sum, elevated circulating corticosterone enhances antipredator responses for all male tree lizard morphs, without altering morph-specific or size-specific differences in their behavioral responses.     

Behavior of Four Species of Fiddler Crabs,Genus Uca,in Southeast Sulawesi,Indonesia

We studied the behaviors of four species of sympatric fiddler crabs on Kaledupa Island, Indonesia. Species differences in activity level, grooming, burrowing and feeding were related to their habitat and food. Uca chlorophthalmus, living in muddy mangrove areas, were inactive and spent most of the time feeding in place. Females fed 50% faster than males and spent more time feeding. U. vocans was the dominant species at the beach in silty sand and was very active. Its feeding rate was about twice that of the former species, females fed more rapidly than males, and many crabs of both sexes fed in droves at the water’s edge during ebb tides. During ebb tides, they spent most of their time feeding, while at flood tide they engaged in a greater variety of activities, including burrow maintenance. They frequently walked while feeding and interacted aggressively. U. tetragonon lived in a pebbly band along one edge of the beach, by a quay. Their feeding rate was comparable in both sexes and slower than that of U. vocans; they fed largely on filamentous algae growing on the quay, which provides better food, and fed faster during flood tide than ebb tide. They spent more time in waving and other sex-related activities, and were seldom aggressive, except during the week of the full moon. Burrowing activities included placing excavated mud balls some distance away from their burrows and re-arranging them. U. dussumieri inhabited the other end of the beach in muddier substrate. They did not have sex differences in feeding rates and their rate of scooping food into their mouths was slow, but feeding claws made multiple pinches of the substrate, thus accumulating more material in each clawful of food.     

Burrow structure and use in the sand fiddler crab, Uca pugilator (Bosc)

Uca pugilator, the sand fiddler crab, constructs two kinds of burrows in protected, sandy upper-intertidal and supratidal substrates on the west coast of Florida. Temporary burrows are built and used as a refuge by non-breeding crabs during high tide periods and at night when crabs cease feeding in the intertidal zone. Breeding burrows are constructed and defended by courting males and are the site of mating, oviposition and the incubation of eggs by females. Up to three ovigerous females may be accommodated in a single breeding burrow, each female sequestered in a separate terminal chamber. The construction and defence of burrows specialized for breeding may be an adaptive response by males to the preferences females exhibit when selecting a breeding site.