Solitary Adult Males Research Articles

Dibutyl phthalate released by solitary female locusts mediates sexual communication at low density

Sex pheromones play a crucial role in mate location and reproductive success. Insects face challenges in finding mates in low-density environments. The population dynamics of locusts vary greatly, ranging from solitary individuals to high-density swarms, leading to multiple-trait divergence between solitary and gregarious phases. However, differences in sexual communication between solitary and gregarious locusts have not been sufficiently explored. Herein, we found that solitary locusts but not gregarious ones heavily rely on a single compound, dibutyl phthalate (DBP), for sexual communication. DBP is abundantly released by solitary female locusts and elicits strong attraction of male solitary and gregarious locusts. Solitary adult males display much higher electrophysiological responses to DBP than adult females. Additionally, LmigOr13 was identified as the DBP-specific odorant receptor expressed in neurons housed in basiconic sensilla. Male LmigOr13-/- mutants generated by CRISPR/Cas9 have low electrophysiological responses and behavioral attraction to DBP in both laboratory and field cage experiments. Notably, the attractiveness of DBP to male locusts becomes more evident at lower population densities imposed by controlling the cage size. This finding sheds light on the utilization of a sex pheromone to promote reproductive success in extremely low-density conditions and provides important insights into alternative approaches for population monitoring of locusts.

Asexuality in Drosophila juvenile males is organizational and independent of juvenile hormone.

Sexuality is generally prevented in newborns and arises with organizational rewiring of neural circuitry and optimization of fitness for reproduction competition. Recent studies reported that sex circuitry in Drosophila melanogaster is developed in juvenile males but functionally inhibited by juvenile hormone (JH). Here, we find that the fly sex circuitry, mainly expressing the male-specific fruitless (fruM ) and/or doublesex (dsx), is organizationally undeveloped and functionally inoperative in juvenile males. Artificially activating all fruM neurons induces substantial courtship in solitary adult males but not in juvenile males. Synaptic transmissions between major courtship regulators and all dsx neurons are strong in adult males but either weak or undetectable in juvenile males. We further find that JH does not inhibit male courtship in juvenile males but instead promotes courtship robustness in adult males. Our results indicate that the transition to sexuality from juvenile to adult flies requires organizational rewiring of neural circuitry.

Population dynamics and conservation status of the white-headed langur in the Chongzuo forest fragments, Guangxi, China

AbstractWe present the results of two population surveys conducted 10 years apart (December 2010–February 2011 and December 2020–January 2021) of the Critically Endangered white-headed langur Trachypithecus leucocephalus in the Chongzuo White-Headed Langur National Nature Reserve, Guangxi Province, China. In the first survey, we recorded 818 individuals in 105 groups and 16 solitary adult males. In the second survey, we recorded 1,183 individuals in 128 groups and one solitary adult male. As a result of government policies, poaching for food and traditional medicine is no longer a primary threat to these langurs. However, severe forest loss and fragmentation caused by human activities could limit any future increase of this langur population.

Polar bear (Ursus maritimus) use of the Cape Bathurst polynya and flaw lead

The Cape Bathurst polynya and flaw lead (CBP) are major, predictable habitat features with ≤15% ice cover in an otherwise ice-covered Beaufort Sea, and thought to provide hunting opportunities for polar bears (Ursus maritimus Phipps, 1774). We assessed 78 adult (female; with and without cubs) and subadult (male and female) polar bears’ use of the CBP from October to June 2007–2014. The CBP was up to 725 km wide in autumn, ice-covered in winter, and <306 km wide in spring. Seventy-nine percent (n = 62) of the bears used the CBP (≥1 location <2.4 km, or one 4 h step length, from the CBP). Use was higher for solitary adult females and subadult males, which travelled faster with low turning angles along wider sections than females with offspring and subadult females. Bears were closest to the CBP during the spring hyperphagia season. Although a wider CBP did not prevent crossing, bears primarily crossed from the coast towards pack ice at locations 53% narrower than areas not crossed. Bears might avoid crossing when it would require a long-distance swim. The CBP affects polar bear ecology by providing hunting habitat and a corridor that could increase prey encounters but may affect movement.

Seasonal variation in herd composition of the Formosan sika deer (Cervus nippon taiouanus) in a forest-grassland mosaic habitat of southern Taiwan

The Formosan sika deer was declared extinct in the wild in Taiwan around 1969. In 1994, a series of reintroductions was initiated in Taiwan’s Kenting National Park. Today a wild population is established in the core area of the Park, and even continues to expand. Between October 2016 to March 2018, we used Unmanned Aerial Vehicles (UAV) to survey the herd composition of the sika deer in the Shuiwaku Grassland, a forest-grassland mosaic habitat inside the park. We completed a total of 56 early morning surveys (range: 2–7 per month) during the study period. The photographs and videos collected by UAV were used to identify the age and/or sex of each individuals recorded, and to generate data on deer group size, sex ratio, age-group ratio for each herd, and solitary animals. Overall, we cumulatively detected 394 non-independent deer groups comprised of 4732 individuals, and an additional 130 solitary animals. We found that outside of the rutting season (February–September), adult females remained in the adjacent forest the majority of the time. When females moved into the grassland, they formed small-stable groups with young deer (average size: 6.7 ± 4.5 during the post-rutting season; 6.3 ± 3.2 during the calving season). Males either occupied mixed sex groups (average size: 18.0 ± 9.1 during the post-rutting season; 13.8 ± 7.3 during the calving season), or formed bachelor groups (average size: 5.6 ± 4.3 during the post-rutting season; 5.7 ± 3.8 during the calving season) in the open grassland during this same period. During the territorial rut, the proportion of solitary adult males increased significantly to 24.2 ± 15.4%, whereas females also formed gregarious but unstable mixed sex groups with males (average size: 17.0 ± 12.0). Although we observed the first newborns in the open grassland in August (2017), the ratio of fawns to adult females was highest (56.8%) in October, suggesting that this may be the optimal time to conduct annual birth rate surveys. Overall, we found sexual segregation was present in the Formosan sika deer largely driven by sex-based differences in habitat preference, and the non-random assortment of sexes in response to their reproductive status.

Solitary individuals in populations of the group-living lizard Ouroborus cataphractus: voluntary or forced?

We compared crevice fidelity among solitary and group-living individuals in a population of the group-living lizard Ouroborus cataphractus. We also compared the incidence of solitary individuals between the sexes and different seasons.We surveyed suitable rocky areas at two sites in the Graafwater district, South Africa, and all O. cataphractus individuals found, whether in groups or solitary, were marked and released back into their crevices. The areas were resurveyed after one month, three months and four months to compare crevice fidelity of solitary and group-living individuals. We found that solitary individuals were significantly less loyal to their rock shelters than individuals living in groups, and that solitary females appeared to be less loyal than solitary males. We found no significant difference in the frequency of solitary adult males in and outside of the mating season. Solitary adult males were significantly smaller in mean body size than group-living adult males, but did not have more scars or other deformities than the latter. We found no significant difference in the frequencies of solitary individuals during the wet and the dry seasons, or in the frequencies of solitary adult males versus solitary adult females recorded during any of the surveys. The significantly lower crevice fidelity displayed by solitary than group-living individuals supports the notion that being in a group must be the optimal situation for individuals of this relatively slow-moving cordylid. Our finding that solitary adult males were significantly smaller in mean body size than group-living adult males also suggests that the exclusion of less competitive males from groups may in part be responsible for the occurrence of solitary males.

Solitary Individuals in Populations of the Group-Living Lizard Ouroborus Cataphractus: Voluntary or Forced?

We compared crevice fidelity among solitary and group-living individuals in a population of the group-living lizard Ouroborus cataphractus. We also compared the incidence of solitary individuals between the sexes and different seasons. We surveyed suitable rocky areas at two sites in the Graafwater district, South Africa, and all O. cataphractus individuals found, whether in groups or solitary, were marked and released back into their crevices. The areas were resurveyed after one month, three months and four months to compare crevice fidelity of solitary and group-living individuals. We found that solitary individuals were significantly less loyal to their rock shelters than individuals living in groups, and that solitary females appeared to be less loyal than solitary males. We found no significant difference in the frequency of solitary adult males in and outside of the mating season. Solitary adult males were significantly smaller in mean body size than group-living adult males, but did not have more s...

Different factors that modify anti-predator behaviour in guanacos (Lama guanicoe)

Animals optimize the trade-off between the cost of not fleeing and the benefits of staying because the factors that influence flight decisions and the disturbance level of a particular stimulus can vary both spatially and temporally. Different factors (human impact and habitat characteristics) likely to modify anti-predator behaviour in different types of guanaco social groups were analysed. We found that group size was conditioned by high poaching, vehicle traffic, predation risk and vegetation density. Solitary adult males showed shorter alert and flight initiation distances than bachelor and mixed groups. Alert distance was greater during the summer season, and assessment times were shorter when young were present in the groups. In high-predation-risk environments, guanacos detected threats at greater distances and flight initiation distance was longer. Alert distances were shorter on steeper sloped hills and assessment times were shorter in areas with irregular topography than on flat sites. In high traffic areas, flight initiation distance was longer and assessment times were shorter. And in areas with low poaching intensity, assessment times were greater than in those with high poaching levels. Therefore, guanacos may be able to evaluate a true threat. Social group and anti-predator responses were conditioned by habitat characteristics and human impact. We consider that plasticity of responses could be key to the survival of guanacos.

Female North Atlantic right whales produce gunshot sounds

North Atlantic right whales (Eubalaena glacialis) produce loud, broadband, short duration sounds referred to as gunshots. The sounds have been hypothesized to function in a reproductive context, as sexual advertisement signals produced by solitary adult males to attract females and/or agonistic displays among males in surface active groups. This study provides evidence that gunshot sounds are also produced by adult females and examines the acoustics and behavioral contexts associated with these calls. Results from boat-based observational surveys investigating the early vocal ontogeny and behavior of right whales in the critical southeast calving habitat are presented for a subset of mothers who produced gunshots while in close proximity to their calves. Of 26 different isolated mother-calf pairs, gunshots were recorded from females of varied ages and maternal experience. The signals were recorded when calves separated from their mothers during curious approaches toward objects on the surface. While the spectral and temporal characteristics of female gunshots resemble those attributed to adult males, these calls were orders of magnitude quieter (Ő30 dB). Relatively quiet gunshots posed minimal risk of injury to nearby calves. The social and behavioral context suggests gunshots were associated with maternal communication and may also be indicators of stress and agitation.

Cooperative vigilance: The guanaco's (Lama guanicoe) key antipredator mechanism

The concept of sociality has been associated with the effectiveness of antipredator mechanisms, like cooperative vigilance and the dilution effect. Lama guanicoe (guanaco) is a social native herbivore in South America and a social species. The objectives of this study were to evaluate the antipredator responses of different-sized groups of guanacos in areas with varying predation risks and to determine antipredator mechanisms in guanacos. For this, we measured different antipredator responses to a potential predator (human subjects). Detection of predator and flight distances from predator both increased with a greater number of guanacos per group and with greater distances among guanacos within the social group. Both buffer distance and flight time decreased with a greater number of guanacos per group, but increased with greater distances among guanacos inside the social group. Solitary adult males moved shorter distance and mixed groups moved greater distances. Flight distances were greater in areas with tall and dense vegetation than in areas with low vegetation. Buffer distance and flight time were shorter in undulating land than on flat lands, and groups were usually observed on hill slopes. Our results suggest that the benefit of social grouping in guanacos is the increased probability of avoiding predator with cooperative vigilance and not with the dilution effect. This means that a predator could be detected earlier when approaching a guanaco group than when approaching a solitary individuals and could thus be avoided.

CURRENT POPULATION STATUS OF THE ENDANGERED ENDEMIC SUBSPECIES OF SWAYNE'S HARTEBEEST (ALCELAPHUS BUSELAPHUS SWAYNEI) IN MAZE NATIONAL PARK, ETHIOPIA

A study on current population status, sex ratio and age structures of Swayne’s hartebeest ( Alcelaphus buselaphus swaynei ) was carried out during 2009/2010 in Maze National Park. Total count method was used in an area of 220 km 2 using well trained park scouts based on silent detection. There were 372 individuals counted. The population trend indicates that there is a significant increase in the number of Swayne’s hartebeest population in Maze National Park at present. The sex ratio of adult males to adult females and young to adult females was 1:1.4 and 1:2.2, respectively. There is no significant difference between the sex ratio of males and females whereas there is a significant difference between young and adult females. Group size of Swayne’s hartebeest varied from solitary individuals to a maximum of 27. The difference among the groups is not significant. More solitary adult males were observed than solitary adult females. Swayne hartebeests were more associated with grassland with scattered trees (54%) than other three habitat types of the area, savannah grassland, bushland and riverine forest. There were no significant differences among the association of habitat types. Hartebeests were more associated to oribi (68%) than other ungulate species. There is an urgent need for further study to evaluate the actual threat of the endangered endemic subspecies of Swayne's hartebeests in Maze National Park.

Familiarity breeds progeny: sociality increases reproductive success in adult male ring-tailed coatis (Nasua nasua)

The ring-tailed coati (Nasua nasua) is the only coati species in which social groups contain an adult male year round, although most males live solitarily. We compared reproductive success of group living and solitary adult male coatis to determine the degree to which sociality affects reproductive success. Coati mating is highly seasonal and groups of female coatis come into oestrus during the same 1-2 week period. During the mating season, solitary adult males followed groups and fought with the group living male. This aggression was presumably to gain access to receptive females. We expected that high reproductive synchrony would make it difficult or impossible for the one group living male to monopolize and defend the group of oestrous females. However, we found that group living males sired between 67-91% of the offspring in their groups. This reproductive monopolization is much higher than other species of mammals with comparably short mating seasons. Clearly, living in a group greatly enhanced a male's reproductive success. At the same time, at least 50% of coati litters contained offspring sired by extra-group males (usually only one offspring per litter); thus, resident males could not prevent extra-group matings. The resident male's reproductive advantage may reflect female preference for a resident male strong enough to fend off competing males.

Mammoths

Mammoths

Hainan Black-crested Gibbon Is Headed For Extinction

Although Hainan black-crested gibbons have been on the list of the most endangered primate species in the world for many years, their environment is still deteriorating, especially on Hainan Island. Our findings indicate that the species is unlikely to survive the next decades unless efficient conservation policies and strategies are put in place immediately. Census data show that populations of the species used to occur across the whole island, but in 2003 only 13 individuals could be found, confined to a small region, the Bawangling Natural Reserve (19∘ 021–19∘ 081N and 109∘ 021–109∘131 E), in the western part of the island, covering only 14–16 km2. In other words, ca. 99% of the habitat has vanished in the past 300 years. Such dramatic change has pushed the species to the edge of extinction; only 2 groups and 2 solitary adult males, remained in 2003. Two adult females, 2 juveniles and one infant comprise Group A, in Dong’er, the core area of the western part of the reserve; and 1 adult male, 2 adult females, 1 juvenile and 1 infant formed another group (B), confined to another core area (Nanchahe) in the northern part of the reserve. The dramatic decline in the gibbon population has occurred due to vegetation reduction, ecological deterioration and extensive human impact. The forest cover was reduced from 95.5% 2000 years ago to just 4% in 1999; and the human population in 2003 was 330% larger than in 1950.

Roosting ecology and social organization of the spotted-winged fruit bat, Balionycteris maculata (Chiroptera: Pteropodidae), in a Malaysian lowland dipterocarp forest

The aims of this study were to investigate the roosting ecology and social organization of the spotted-winged fruit bat, Balionycteris maculata (Megachiroptera), within an old-growth Malaysian dipterocarp forest, and test the hypothesis that males spend a significantly greater proportion of the night in the immediate vicinity of their day roosts than females. Balionycteris maculata roosted in cavities and formed small harem groups that consisted of one adult male accompanied by up to nine adult females and their dependent young. Both male and female bats foraged locally, within approximately 1 km of their roost sites. However, in contrast to females, which remained away from the roost site throughout the night, both harem and solitary adult males divided their nightly activity between foraging and returning to their roost sites. Individual females were also found roosting sequentially with up to three different males. Hence, these results suggest that B. maculata has a resource-defence polygynous mating system, in which the roost cavity may represent a critical and defendable resource by which males recruit and gain improved reproductive access to females. Roost cavities occupied by B. maculata were found within a number of different forest structures, including ant nests, termite nests and the root masses of epiphytes. The consistent shape and position of the cavities, along with a single observation of cavity enlargement, provide the first evidence of roost-cavity excavation, by a megachiropteran bat, within the nests of social insects. Although the cues by which females select their roost sites are unclear, some aspect of roost cavity size, or condition, may provide a possible means by which females can assess the reproducÍtive fitness of potential mates.

Survey of the black howler monkey, alouatta pigra, population at the Mayan site of Palenque, Chiapas, Mexico.

A survey of the population of the black howler monkey (Alouatta pigra) present at the Mayan site of Palenque was conducted during 2000. A total of 911 man/hours, spread over 112 days were spent surveying the 600 ha area of pristine forest at the site for howler troops. We detected the presence of 136 individuals of which 131 were members of 20 troops, the rest were 3 solitary adult males and 2 adult males travelling as a pair. Ecological density was estimated at 23 individuals/km(2). Mean troop size was 7.0 individuals and it ranged from 2 - 12 individuals; 60% of the troops were multimale. All sighting of howler monkeys were in evergreen rain forest and 75% were in trees > or = 20 m in height. The reported densities and mean troop size are higher than those reported for the species in Guatemala and in central Quintana Roo, Mexico. The vegetation of the forest contains tree species reported to be used by species of Alouatta in the Moraceae, Sapotaceae, Leguminosae, and Lauraceae plant families. Protection of a large perimeter area (ca 1700 ha) around the archeological site by the Mexican government ensures the conservation of the forest and of the black howler monkey population present at the site.

HABITAT SELECTION, HOME RANGE, AND ACTIVITY OF THE WHITE-NOSED COATI (NASUA NARICA) IN A MEXICAN TROPICAL DRY FOREST

We investigated how white-nosed coatis (Nasua narica) cope with the extreme seasonality of a Mexican tropical dry forest by studying their activity, home ranges, and habitat selection in relation to climatic seasonality. From November 1994 to March 1997, we radiotracked 7 solitary adult males and 11 bands of females and juveniles. Males extended their activity more into night hours, were more active in both the dry and the wet seasons, and traveled a greater daily distance during the wet season than groups of coatis. Average total home range was 383.0 ha ± 32.86 SE and did not differ between sexes. Home ranges differed seasonally only in groups that used areas during the dry season that were twice as large as those used during the wet season. Three major habitats that differed in phenology were used by coatis. Both males and groups preferred arroyo forest to dry forest and semideciduous forests. These results illustrate the importance of behavioral traits that permit coatis to have access to habitats where sparse resources (e.g., food and water) are more available as a mechanism to cope with climatic seasonality. Our study provides a basis for design of management and conservation strategies for the Chamela–Cuixmala Biosphere Reserve. The population of coatis in this reserve may be considered as a model to predict the type of behavioral responses that other populations of coatis may use to cope with climatic seasonality in other tropical dry forests throughout México and Central America.

Social Organization of the Babirusa (Babyrousa babyrussa) and Their Use of Salt Licks in Sulawesi, Indonesia

The babirusa ( Babyrousa babyrussa ), an endangered suid endemic to Sulawesi, Indonesia, has scarcely been studied in the wild. Sixty hours of observation on social organization of babirusa and patterns of visitation to a natural salt lick were made during 32 months in 1989–1994. Babirusa groups observed at the lick were 1–13 individuals ( n = 393 groups), and solitary adult males or matriarchal groups were the most frequently sighted group types. A daily pattern of visits to the lick was discernible with the highest number of groups at the lick between 1700–1800 h. Mean duration of visit was greatest (17.4 min) between 1700–1800 h. Use of the lick differed markedly among mammalian species; 98.0% of all activity was of babirusa compared with <1.0% by each of three other endemic Sulawesi mammals. Chemical analysis of soil and water at the lick revealed higher levels of minerals than in control samples. Possible reasons for geophagy by babirusa are discussed.

The social organization of mountain gazelles Gazella gazella in a population reintroduced to central Arabia

Two years after mountain gazelles were released in central Arabia, the social organization of the reintroduced population was similar to that of wild populations. It was uninfluenced by the captive origins of the population's founders, which are now a minority of the study population. The more common social groupings were solitary adult males (20% of groups), groups of males (13%), solitary adult females (14%), and groups of females and juveniles, either with (14%) or without (27%) an adult male. The companions of a female were determined primarily by her reproductive status. Adult females were often alone (18% of individual females), especially around the time of parturition, or accompanied by just a juvenile (22%), or just an adult male (5%), or both (5%). Sometimes, their companions included one (27% of individuals) or two (11%), and rarely three or four, other females and their juveniles. Some adult males were territorial and they were usually solitary (58% of days) or with females (38% of days). Subadult males and non-territorial adult males formed bachelor groups, which rarely associated with females. The largest group of gazelles comprised 11 males, but more than 72% of all sightings were of solitary gazelles or groups of two. Rainfall was low (<125 mm annually) and seasonal, but runoff accumulated in wadis and was stored in the subsoil. Consequently, food availability for gazelles in the wadis, although low, was less seasonally-variable than rainfall. Territories were maintained throughout the year and there was little seasonal variation in group composition, although female groups were often larger during winter than in summer. Differences in total rainfall between years also had no obvious effect on social organization, which varied little between 1993 and 1994, although rainfall during the winters at the start of these years varied five-fold.

Population ecology of the white‐nosed coati (Nasua narica) on Barro Colorado Island, Panama

The white‐nosed coati, Nasua narica, is a common Neotropical carnivore with a social structure of band‐living adult females and solitary adult males. A coati population on Barro Colorado Island, Panama, was studied over a four‐year period by mark‐recapture, radiotelemetry. and direct observation of habituated individuals. The population density was approximately 51.5 individuals/km2 and the sex ratio was 1:1. Band size varied from six to 26 individuals (mean = 15.3) with extensive fluctuation within and between years. Mean foraging group size was smaller (7.2 individuals) than population group size, and fluctuated with food availability, synchronous parturition, and the emigration of mature males. Mean home‐range size of six bands was 0.33 km2, and ranges of adjacent bands overlapped from 0–66%. One band fissioned during the study; however, the resulting bands did not disperse from the original home range. Seven adult males had a mean home‐range size of 0.37 km2, each extensively overlapping the home ranges of several other males. Observations of 10 adult males whose natal bands were known indicate that when males disperse they do not simultaneously leave the band's home range. Rather, their home ranges remain within or broadly overlapping those of their natal bands. This dispersal pattern is unusual within the order Carnivora.