Effects of exposure to predatory cues on territorial behaviour of male fathead minnows

We conducted a laboratory study to determine if male fathead minnows, Pimephales promelas, altered their territorial behaviour associated with reproduction in response to combinations of visual and chemical cues from northern pike, Esox lucius. We introduced the following stimuli to a territorial male: a brick (control), fathead minnow alarm pheromone, a pike fed brook stickleback, Culea inconstans, or a pike fed fathead minnow. The territorial behaviour of males did not change when the control was added. Male minnows experiencing threat from pike fed stickleback significantly reduced the frequency at which they performed three territorial behaviours, but, within 12 h, had returned to pre-exposure activity levels. Male minnows subjected to alarm pheromone alone and to pike fed fathead minnow significantly reduced their territorial behaviour, abandoned their nests, and did not return to pre-exposure levels of activity after 24 h. We suggest that because risk of predation triggers prolonged decreases in territorial defense, it may affect competition between nesting males and female mate choice. We conclude that fathead minnows can assess the severity of predatory threat and adjust their reproductive behaviour accordingly.     

Aggressive Transition between Alternative Male Social Tactics in a Long-Lived Australian Dragon (Physignathus lesueurii) Living at High Density

Theory predicts the evolution of alternative male social tactics when intense competition coupled with the superior competitive ability of some individuals limits access to reproductive opportunities by others. How selection has shaped alternative social tactics may be especially interesting in long-lived species where size among sexually mature males varies markedly. We conducted experimental studies on long-lived eastern Australian water dragons living where competition was intense to test the hypotheses that mature males adopt alternative social tactics that are plastic, and that large size and body condition determine resource-holding potential. Approximately one-half of mature males (N = 14) defended territories using high rates of patrol and advertisement display, whereas 16 smaller mature males having lower body condition indices utilized non-territorial social tactics. Although territorial males were larger in absolute size and head dimensions, their heads were not allometrically larger. Territorial males advertised very frequently using displays involving stereotypical movements of the head and dewlap. More aggressive displays were given infrequently during baseline social conditions, but increased during periods of social instability. Female home ranges overlapped those of several territorial and non-territorial males, but females interacted more frequently with territorial males. The extreme plasticity of social tactics in this species that are dependent on body size was confirmed by two instances when relatively large non-territorial males spontaneously evicted territory owners, and by marked shifts in tactics by non-territorial males in response to temporary experimental removals of territory owners, followed (usually) by their expulsion when original owners were reinstated. The high level of social plasticity in this population where same-sex competitors are densely concentrated in preferred habitat suggests that chronic high energetic costs of defense may select for males to cycle between territorial and non-territorial social tactics depending upon their changing energetic status and their current capacity for competition with rivals.     

The effects of social isolation on steroid hormone levels are modulated by previous social status and context in a cichlid fish

Social isolation is a major stressor which impacts the physiology, behaviour and health of individuals in gregarious species. However, depending on conditional and contextual factors, such as social status and group composition, social isolation may be perceived differently by different individuals or even by the same individuals at different times. Here we tested the effects of social status (territorial vs. non-territorial) and previous group composition (i.e. type of social group: mixed sex group with two territorial males, TT vs. mixed sex group with one territorial and one non-territorial male, TnT) on the hormonal response (androgens and cortisol) to social isolation in a cichlid fish (Oreochromis mossambicus). The different steroid hormones measured responded differentially to social isolation, and their response was modulated by social factors. Social isolation elicited a decrease of 11-keto formation only in territorial males, whereas non-territorial males present a non-significant trend for increasing KT levels. Testosterone did not respond to social isolation. Cortisol only increased in isolated individuals from TnT groups irrespective of social status (i.e. both in territorials and non-territorials). These results suggest that it is the perception of social isolation and not the objective structure of the situation that triggers the hormonal response to isolation.     

Seasonal dynamics of agonistic displays in territorial and non-territorial males of goitered gazelle

Aggression serves a great variety of social functions, one of which is protection of individual territories from intruders. Territorial males of many antelope species show aggressive noncontact displays, and only rarely fight. It has been suggested that ungulate males tend to have more frequent and longer aggressive interactions with rivals of similar age or social status than with males of dissimilar status. In the present paper, we test whether territorial and non-territorial males behave in a similar manner and avoid fights, and whether or not they preferentially direct aggressive and longer agonistic interactions towards males of similar age or social status, rather than towards other classes of males. We found that territorial males usually avoided straight fights with peers, and instead mainly used noncontact displays in aggressive interactions. In contrast, non-territorial males used fights considerably more often, especially during the onset of territoriality in April to May, when these males had their most frequent aggressive interactions. Territorial bucks aggressively interacted most frequently with non-territorial males and significantly less often with other territorial males, but agonistic noncontact displays between territorial males lasted the longest. In contrast, non-territorial males addressed their aggressive noncontact displays and fights most often to peers and less frequently to sub-adults. Asymmetry in the social status of territorial vs. non-territorial males was likely responsible for the distinctively different agonistic behaviors shown by the two types of males, which in turn are likely due to the different costs and benefits each male can accrue from these aggressive interactions.     

Male urine signals social rank in the Mozambique tilapia (Oreochromis mossambicus)

Background  

The urine of freshwater fish species investigated so far acts as a vehicle for reproductive pheromones affecting the behaviour and physiology of the opposite sex. However, the role of urinary pheromones in intra-sexual competition has received less attention. This is particularly relevant in lek-breeding species, such as the Mozambique tilapia (Oreochromis mossambicus), where males establish dominance hierarchies and there is the possibility for chemical communication in the modulation of aggression among males. To investigate whether males use urine during aggressive interactions, we measured urination frequency of dye-injected males during paired interactions between size-matched males. Furthermore, we assessed urinary volume stored in the bladder of males in a stable social hierarchy and the olfactory potency of their urine by recording of the electro-olfactogram.     

A multidisciplinary study on social status and the relationship between inter-individual variation in hormone levels and agonistic behavior in a Neotropical cichlid fish

Social animals with hierarchal dominance systems are particularly susceptible to their social environment. There, interactions with conspecifics and hierarchal position can greatly affect an individual's behavior, physiology and reproductive success. Our experimental model, Cichlasoma dimerus, is a serially-monogamous Neotropical cichlid fish with a hierarchical social system, established and sustained through agonistic interactions. In this work, we aimed to describe C. dimerus social structure and its association with hormonal profiles and testicular cellular composition. We recorded and quantified agonistic interactions from the territorial pair, i.e. the top ranked male and female, and the lowest ranked male of stable social groups. Plasma levels of 11-ketotestosterone (11-KT), testosterone, 17β-estradiol (E₂) and cortisol were measured by ELISA. Results show that territorial pairs cooperatively guarded the territory, but rarely attacked in synchrony. Territorial males had higher testosterone and 11-KT plasma levels than non-territorial males, while E₂ and an index of its metabolization from testosterone were higher in non-territorial males. No difference was observed in cortisol levels. Plasma 11-KT and an index of the conversion of testosterone to 11-KT, positively correlated with the frequency of aggressiveness, while E₂ showed the opposite pattern. Territorial males had a higher gonadosomatic index than non-territorial males. The quantification of testicular cellular types revealed that the percentage of spermatocytes and spermatids was higher in non-territorial males, while territorial males showed a greater percentage of spermatozoa. Thus, C. dimerus male social position within a stable hierarchy is associated with distinct behaviors, steroid levels and testicular degree of development.     

Male Cheetah Social Organization and Territoriality

Patterns of territory ownership in male cheetahs inhabiting the Serengeti Plains are described, and factors affecting territorial behaviour are examined. Body size and age were factors influencing whether males became territorial, and single males usually had to join up with others in order to oust residents. Both size of male coalition and body size of its members were associated with length of tenure on territories. Limited data suggest that territory owners were probably no more likely to encounter females than were non-territorial males but there was a suggestion that they suffered lower survivorship costs than non-territorial males.     

Male dimorphism, territoriality and mating success in the tropical damselfly, Paraphlebia zoe Selys (Odonata: Megapodagrionidae)

The tropical damselfly Paraphlebia zoe has two male morphs: a black-winged (BW) male which is associated with territorial defense of oviposition sites; and a hyaline-winged (HW) male similar in appearance to females, and, compared to the black morph, less frequently found defending territories. In a wild population of this species, we first assessed the relationship between phenotypic traits [male morph, size and territorial status (being territorial or non-territorial)], their role on mating success, and the degree to which a particular territory may contribute to male mating success. Second, to relate a physiological basis of being territorial we compared both morphs in terms of muscular fat reserves and thoracic muscle, two key traits related to territory defense ability. Males of both morphs defended territories although the BW males were more commonly found doing this. BW males were larger than HW males and size predicted being territorial but only within HW males (territorial males were larger) but not in BW males. Male mating success was related to territorial status (territorial males achieved a higher mating success), but not to morph or size. Furthermore, territory identity also explained mating success with some territories producing more matings than others. The BW morph stored more fat reserves which may explain why this morph was more likely to secure and defend a place than the HW morph. However, the HW morph showed higher relative muscle mass which we have interpreted as a flexible strategy to enable males to defend a territory. These results are distant to what has been found in another male dimorphic damselfly, Mnais pruinosa, where the advantage of the non-territorial morph relies on its longevity to compensate in mating benefits compared to the territorial morph.     

Endocrine status affects bladder size and postvoid residual urinary volume in mice

Urine is one of the major media for intraspecific chemical communication in mice. The urination pattern is dependent both on the mice's hormonal and social status. The urination pattern and the morphology of the urinary tract were examined in mice following hormonal manipulations. In the first experiment, we compared pairs of intact and castrated males: intact males urinated earlier when exposed to a new environment, with a greater number of drops that were smaller than those of castrated males. In the second experiment, groups of intact males, castrated, testosterone-supplemented castrated, and isolated intact males were compared. The micturition pattern of isolated intact males consisted of numerous small droplets of urine, with a high volume of urine retained in the bladder after voiding. This also applied to grouped intact males and testosterone-treated castrated mice, while castrated mice voided a larger fraction of bladder content. Bladder weight was higher in intact males and testosterone-treated castrated males, as compared to castrated males. In the third experiment, ovary-intact and testosterone-treated intact females were compared. Testosterone-treated ovary-intact females retained a larger quantity of urine in the bladder and also had a larger bladder compared to ovary-intact females. Testosterone thus induces the morphological modifications of the urinary tract necessary for the dominant male urination pattern, which is an increase in postvoid urinary residual volume and bladder weight. As evidenced from the comparison of histological sections from intact, castrated, and testosterone-treated castrated males, the increase in bladder weight was mainly due to the bladder muscular mass.     

Variations of space use in males of the banded demoiselle (<Emphasis Type="Italic">Calopteryx splendens</Emphasis>, Zygoptera,Odonata): Alternative tactics or an age-dependent trend?

Two spatial tactics are usually distinguished in males of Calopteryx damselflies: territorial and nonterritorial. These tactics are believed to underlie two alternative condition-dependent reproductive tactics in these insects, and territorial males are believed to copulate more often. With age, males become weaker, turn nonterritorial, and only occasionally manage to copulate. However, the details of space use by damselflies are poorly known, which hinders the interpretation of the existing empirical data. We describe the space use by individually marked males of the banded demoiselle C. splendens studied during three field seasons in Vladimir Province, Russia. Each male on each day of observations was characterized as either territorial or non-territorial, and the sites of encounter were mapped. The probability of being territorial declined with the male’s age. The spatial tactics (territorial vs. non-territorial) on a given day strongly influenced the tactics used on the following day. We identified the territorial and non-territorial phases in the life of a male damselfly, which occurred consecutively and had a roughly similar duration. During the territorial phase, the male occupied a certain territory and tried to hold it as long as possible. The male abandoned its territory in two cases: (1) when it was driven onto a different territory as the result of competition with other males, or (2) when it was exhausted and became non-territorial. Thus, the space use by the male changed predictably during its life. Therefore, direct comparison of morphological or other characteristics in territorial vs. non-territorial males, frequently made in the literature, makes little sense. Further progress in studying the so-called “alternative reproductive tactics” in damselflies may be more successfully achieved by comparing individual life trajectories of different males (e.g. duration of territorial and non-territorial periods, the number of consecutively occupied territories, etc.). We performed correlation analysis and found that the above parameters did not depend on the wing and abdomen length of the males.     

Territoriality and nutritional condition in Cynotilapia afra (Gunther) and Pseudotropheus zebra (Boulenger), cichlidae in Lake Malawi National Park, Malawi

The standard length, diurnal activities, territory sizes, and areas over which individuals foraged and the nutritional condition of territorial and non-territorial Cynotilapia afra and Pseudotropheus zebra were compared. Results show that territorial tenureship in these fishes does not depend on the male size, implying that aggressiveness, experience and motivation are more important in the maintenance of territory. However, terri-toriality in C. afra (t = 10.93, P < 0.05) and P. zebra (t = 3.31, P < 0.05) manifests itself in the reduction of nutritional condition because territorial males engage in energetically more demanding activities, e.g. courtship displays, fertilizing ripe females and chasing intruders that trespass into their territories. Territorial C. afra (t = 4.77; P < 0.05) and P. zebra (t = 5.89; P < 0.05) also fed over significantly smaller areas and spent significantly less time feeding than did non-territorial males. The biological significance of territoriality in these fish species is therefore not food intake, but mate attraction and reproductive success for which they trade off their nutritional condition. However, there might be a nutritional threshold below which the cost out-weighs the benefit. Hence, territorial males in poorer health abandon their territories in order to regain their condition.     

The adaptive significance of non-contact mate guarding by males of the dragonfly,Nannophya pygmaea Rambur (Odonata: Libellulidae)

InNannophya pygmaea, ovipositing females were frequently disturbed by conspecific males. Disturbed females often copulated with one of these males or flew away from the pool. Females which flew away from the pool due to male disturbance often returned later the same day and mated with different males. A territorial male would guard his ovipositing mate by hovering above her, presumably trying to prevent her from moving out of his territory. A non-territorial male would also guard his mate in a similar way, both at a vacant water area which was not occupied by any territorial males, or within the territory of a resident male. In addition, both territorial and non-territorial males chased intruding males in an attempt to prevent their mates from being stolen. Territorial males defended their mates better than non-territorial males. Both males and females often mated more than once in the course of a single day. Some territorial males copulated with a new female while another mate oviposited in their territories. This observation supported the “multiple mating hypothesis” proposed by Alcock (1979) and Uéda (1979) but other evidence suggested that this is an inadequate explanation for the non-contact guarding ofN. pygmaea.     

Territorial status and survival in red grouse Lagopus lagopus scoticus: hope for the doomed surplus?

A previous study of survival in territorial and non-territorial red grouse Lagopus lagopus scoticus conducted between 1957 and 1967 found that territorial status in the autumn pre-determined over-winter survival. A very high proportion of territorial birds survived and virtually all non-territorial birds died or emigrated. We tested the hypothesis that over-winter survival was dependent on territorial status within four grouse populations in Scotland between 1986 and 1993. In contrast to the previous study, 66% of non-territorial birds survived over winter compared to approximately 70% of territorial birds. There was no significant effect of territorial status on the survival estimates. Moreover, some of the birds considered to be non-territorial during autumn went on to successfully raise a brood. We suggest that on our study sites, territory ownership in autumn did not greatly influence over-winter survival, and territorial behaviour did not determine breeding density as previously supposed. We postulate differences with other studies may reflect variations in scale and predation pressure.     

Reproductive success in male Japanese minnows,Pseudorasbora parva: observations under experimental conditions

To evaluate the spawning success of male Japanese minnows,Pseudorasbora parva, and female mate choice, spawning behaviour was observed under both artificial and experimental conditions. Larger males had larger territories and greater reproductive success. The body weight of territorial males decreased during the maintenance of territories, while that of non-territorial males increased significantly. When the weight of non-territorial males exceeded that of territorial males, the former began to establish new territories on the substrate, suggesting a conditional strategy by non-territorial males to trade off immediate reproductive success with growth and hence improve future reproductive success. Females chose males with larger body size, probably based on dominance rank rather than the quality (or size) of territory. It was concluded that females choose males of higher dominance rank and that males compete for large territories, both of which play an important part in male reproductive success.     

Testis-testicular gland complex of two Tripterygion species (Blennioidei, Teleostei): differences between territorial and non-territorial males

The morphological differences between the testis and testicular gland of territorial and nonterritorial males of Tripterygion tripteronotus and T. delaisi were examined and correlated with differences in reproductive behaviour. In territorial males of both species the testicular gland is much more developed than in non-territorial males. Larger cellular and nuclear sizes in the territorial males indicate that the activity of the gland cells is enhanced. These cells contain SER, numerous lipid droplets and mitochondria with lamellar cristae. Absence of 3β-HSD activity at these sites points to lack of a steroidogenic potency. In both territorial and non-territorial fish, steroid-producing Leydig cells have been demonstrated in the connective tissue betweeen the testis and the testicular gland, and around the collecting sperm duct. In addition, 3β-HSD activity has been found in the scarce interstitial Leydig cells of territorial fish. Morphometric data indicate an enhanced activity of the Leydig cells in territorial fish.     

A hypothetico-deductive approach to assessing the social function of chemical signalling in a non-territorial solitary carnivore

The function of chemical signalling in non-territorial solitary carnivores is still relatively unclear. Studies on territorial solitary and social carnivores have highlighted odour capability and utility, however the social function of chemical signalling in wild carnivore populations operating dominance hierarchy social systems has received little attention. We monitored scent marking and investigatory behaviour of wild brown bears Ursus arctos, to test multiple hypotheses relating to the social function of chemical signalling. Camera traps were stationed facing bear 'marking trees' to document behaviour by different age sex classes in different seasons. We found evidence to support the hypothesis that adult males utilise chemical signalling to communicate dominance to other males throughout the non-denning period. Adult females did not appear to utilise marking trees to advertise oestrous state during the breeding season. The function of marking by subadult bears is somewhat unclear, but may be related to the behaviour of adult males. Subadults investigated trees more often than they scent marked during the breeding season, which could be a result of an increased risk from adult males. Females with young showed an increase in marking and investigation of trees outside of the breeding season. We propose the hypothesis that females engage their dependent young with marking trees from a young age, at a relatively 'safe' time of year. Memory, experience, and learning at a young age, may all contribute towards odour capabilities in adult bears.     

On Social Organization and Behaviour of the Gerenuk Litocranius walleri (Brooke 1878)

The social organization of the gerenuk in Tsavo East National Park, Kenya, is characterized by single adult ♂♂ on territories encompassing their entire home ranges, small ♀-groups of variable composition, often associated with territorial ♂♂, and small groups of subadult ♂♂. There appear to be no non-territorial adult ♂♂ (“bachelors”). Subadult ♂♂ wander about considerably, often alone, before they succeed in taking over a territory. Territorial ♂♂ perform linked urination/defecation and mark dry twigs with the antorbital gland secretion. Agonistic and courtship behaviour resemble those of other gazelles. Mother-young relations conform to the “hider type” among bovids.     

Histomorphology of preorbital gland in territorial and non-territorial male blackbuck Antelope cervicapra, a critically endangered species

The preorbital gland is a specialized dermal gland of antelopes which plays an important role in territorial marking behavior and pheromonal communication. To our knowledge, there is little information available on the role of preorbital gland marks in Indian antelopes (blackbucks). Males are seen averting the gland during behavioural display and territorial marking but the functional aspect of this gland has not been examined. Hence, the aim of this study was to describe the histomorphology of the preorbital gland in territorial and non-territorial male blackbucks to determine its morphology and secretory function. The results showed that the preorbital gland is composed of modified sebaceous and apocrine glands. The apocrine gland is lined by simple cuboidal epithelial cells; the serous parts of the secretory products are often seen in the apical portions of the cells. The myoepithelial cells contain actin filaments lying on the basal membranes of the apocrine gland. There are some considerable histological changes in the presence of the sebaceous and apocrine glands in territorial males in comparison to non-territorial males. The following histological changes associated with occurrence of the sebaceous and apocrine glands have been observed in territorial and non-territorial male blackbucks: (1) increase of size of sebaceous and apocrine glands and (2) increase in density of sebaceous and apocrine glands in territorial males compared to non-territorial males. It is suggested that the higher development (i.e., size) and density of sebaceous and apocrine glands in territorial males could depend on hormone production (i.e., testosterone). Based on the histological observation and the role of sebaceous and apocrine glands in the preorbital gland supported by literature, it is possible to conclude that both territorial and non-territorial blackbuck males may produce pheromonal substances through preorbital gland (secretion) for olfactory communication.     

Urinary androgen concentrations and social status in two species of free ranging zebra (Equus burchelli and E. grevyi)

In both species of zebra, breeding males had higher urinary androgen concentrations (ng androgens/mg Cr) than did non-breeding bachelor males (30.0 +/- 5.0 (N = 9) versus 11.4 +/- 2.8, (N = 7) in the plains zebra; 19.0 +/- 2.2 (N = 17) versus 10.7 +/- 1.2 (N = 14) in the Grevy's zebra). In the more stable family structure of the plains zebra (single male non-territorial groups) variations in androgen concentrations could not be ascribed to any measured variable. In the Grevy's zebra, androgen values were significantly lower in samples taken from territorial (breeding) males which had temporarily abandoned their territories (N = 4) and the urinary androgen concentration for a male on his territory was negatively correlated with the time since females last visited the territory.