Unpaired Individuals Research Articles

Genetic associations between executive functions and intelligence: A combined twin and adoption study.

Much debate has concerned the separability of executive function abilities and intelligence, with some evidence that the 2 constructs are genetically indistinguishable in children and adolescents but phenotypically and genetically distinct in older adolescents and adults. The current study leveraged data from twin and adoption studies to examine executive function's genetic structure in adulthood (M = 33.15 years, SD = 4.96) and its overlap with intelligence. 1,238 individuals (170 MZ twin pairs, 154 DZ twin pairs, 95 biological sibling pairs, 80 adoptive sibling pairs, and 240 unpaired individuals) completed 6 executive function tasks as well as the Weschler Adult Intelligence Scale-III as part of the Colorado Adoption/Twin study of Life span behavioral development and cognitive aging (CATSLife). Results replicated the unity/diversity model of executive function that distinguishes general executive function abilities (Common EF) from abilities specific to working memory updating (Updating-specific) and mental set shifting (Shifting-specific). In the final model, broad-sense heritability was high for Common EF (h² = .72), Updating-specific (h² = 1.0), and Shifting-specific (h² = .60) factors, as well as for full-scale intelligence (h² = .74). Intelligence was phenotypically and genetically correlated with Common EF (r = .49, broad-sense rg = .44) and Updating-specific (r = .60, rg = .69) abilities. This study represents the first executive function study to apply the adoption design. Leveraging the combined twin and adoptive design allowed us to estimate both additive and nonadditive genetic effects underlying these associations. These findings highlight the commonality and separability of executive function and intelligence. Common EF abilities are distinct from intelligence in adulthood, with intelligence also strongly associated with Updating-specific abilities. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Contact calls in woodpeckers are individually distinctive, show significant sex differences and enable mate recognition

Vocal communication of woodpeckers has been relatively little studied so far, mostly because majority of species use drumming to communicate. Our recent study on the Middle Spotted Woodpecker revealed that a call which is specific for floaters is individually distinctive and functions as a vocal signature of unpaired individuals. The aim of the current study is to investigate whether a contact call of paired territory owners of the same species enables discrimination of individuals and their sex. Acoustic analyses revealed that the call is individually distinctive and experimental approach confirmed that woodpeckers are able to distinguish between a contact call of their partner and a stranger. We also found that the contact call shows significant sex differences. Interestingly, the acoustic parameter enabling sex identification is different than the parameters coding individual variability of the call. The design of a call so that its first part would code the identity of an individual and the second part would code its sex presents an effective and fine-tuned communication system. The results of our study also suggest that the contact call of paired Middle Spotted Woodpeckers may be useful for conservation biologists as a tool supporting other census methods.

Different stress from parasites and mate choice in two female morphs of the blue-tailed damselfly

In Odonates, female colour polymorphism is common and implies the presence of two or more female types with different colours and behaviours. To explain this phenomenon, several hypotheses have been proposed that consider morph frequency, population density, the presence of parasites, and mating behaviour. We studied the blue-tailed damselfly Ischnura elegans, a species with a blue androchrome morph and two gynochrome morphs (the common green infuscans, and the rare orange rufescens-obsoleta). The size of adult males and females, the presence of parasites, and pairing behaviour between males and the three female morphs was assessed in field conditions throughout the reproductive season in NW Italy. Moreover, growth and emergence success of larvae produced by the different morphs was analyzed in standardized conditions. In the field, males showed a preference for the gynochrome infuscans females, despite a similar frequency of androchrome females. In test conditions, male preference for the infuscans females was also observed. Paired males and paired androchrome females were larger than unpaired individuals, while there were no differences in size between paired and unpaired infuscans females. Males and androchrome females were more parasitized than infuscans females. The survival and emergence success of larvae produced by androchrome females was higher than those of offspring produced by the infuscans females. Our results suggest that a higher survival of progeny at the larval stage could counterbalance the higher parasitism and the lower pairing success of andromorph adult females and highlight the importance of considering the whole life-cycle in polymorphism studies.

Home range use in the West Australian seahorse Hippocampus subelongatus is influenced by sex and partner\u2019s home range but not by body size or paired status

Genetic monogamy is the rule for many species of seahorse, including the West Australian seahorse Hippocampus subelongatus. In this paper, we revisit mark-recapture and genetic data of H. subelongatus, allowing a detailed characterization of movement distances, home range sizes and home range overlaps for each individual of known sex, paired status (paired or unpaired) and body size. As predicted, we find that females have larger home ranges and move greater distances compared to males. We also confirm our prediction that the home ranges of pair-bonded individuals (members of a pair known to reproduce together) overlap more on average than home ranges of randomly chosen individuals of the opposite or same sex. Both sexes, regardless of paired status, had home ranges that overlapped with, on average, 6–10 opposite-sex individuals. The average overlap area among female home ranges was significantly larger than the overlap among male home ranges, probably reflecting females having larger home ranges combined with a female biased adult sex ratio. Despite a prediction that unpaired individuals would need to move around to find a mate, we find no evidence that unpaired members of either sex moved more than paired individuals of the same sex. We also find no effect of body size on home range size, distance moved or number of other individuals with which a home range overlapped. These patterns of movement and overlap in home ranges among individuals of both sexes suggest that low mate availability is not a likely explanation for the maintenance of monogamy in the West Australian seahorse.

Uniformly accurate nonlinear transmission rate models arising from disease spread through pair contacts.

We derive and asymptotically analyze mass-action models for disease spread that include transient pair formation and dissociation. Populations of unpaired susceptible individuals and infected individuals are distinguished from the population of three types of pairs of individuals: both susceptible, one susceptible and one infected, and both infected. Disease transmission can occur only within a pair consisting of one susceptible individual and one infected individual. We use perturbation expansion to formally derive uniformly valid approximations for the dynamics of the total infected and susceptible populations under different conditions including combinations of fast association, fast transmission, and fast dissociation limits. The effective equations are derived from the fundamental mass-action system without implicitly imposing transmission mechanisms, such as those used in frequency-dependent models. Our results represent submodels that show how effective nonlinear transmission can arise from pairing dynamics and are juxtaposed with density-based mass-action and frequency-based models.

Middle Spotted Woodpecker territory owners distinguish between stranger and familiar floaters based on their vocal characteristics

Acoustic communication is an important part of behaviour in many bird taxa. In most woodpecker species drumming functions in mate attraction and territory defence. However, woodpeckers also produce calls, which function has been less studied to date. Unlike other woodpeckers, the Middle Spotted Woodpecker Dendrocoptes medius, which is the subject of our study, drums very rarely. Instead, it uses a number of calls, which functions have not been tested to date. We aimed our study at the identification of different calls and assessing their function, both by observation of spontaneous interactions between individuals and playback experiments. We distinguished three calls of different spectral characteristics and functions. Call-1 was mostly uttered by individuals sitting on the branch or a trunk. It was an initial response of territorial pairs to any disturbance within a territory. It signals general anxiety and/or arousal of territorial individuals. Call-2 was mostly uttered by the individuals during flight and it accompanied territorial conflicts and trials to remove the intruder from the territory. It warns the intruder about a territory owner’s readiness to a direct fight. Call-3, characteristic for floaters, was a persistent vocalisation without any obvious stimulus. Acoustic analyses of call-3 revealed that it was individually distinctive and the experimental approach confirmed that woodpeckers were able to distinguish between calling floaters. Thus, Call-3 functions as a vocal signature of unpaired individuals.

Seasonal differences of corticosterone metabolite concentrations and parasite burden in northern bald ibis (Geronticus eremita): The role of affiliative interactions.

The reproductive season is energetically costly as revealed by elevated glucocorticoid concentrations, constrained immune functions and an increased risk of infections. Social allies and affiliative interactions may buffer physiological stress responses and thereby alleviate associated effects. In the present study, we investigated the seasonal differences of immune reactive corticosterone metabolite concentrations, endoparasite burden (nematode eggs and coccidian oocysts) and affiliative interactions in northern bald ibis (Geronticus eremita), a critically endangered bird. In total, 43 individually marked focal animals from a free-ranging colony were investigated. The analyses included a description of initiated and received affiliative interactions, pair bond status as well as seasonal patterns of hormone and endoparasite levels. During the reproductive season, droppings contained parasite eggs more often and corticosterone metabolite levels were higher as compared to the period after reproduction. The excretion rate of endoparasite products was lower in paired individuals than in unpaired ones, but paired animals exhibited higher corticosterone metabolite concentrations than unpaired individuals. Furthermore, paired individuals initiated affiliative behaviour more frequently than unpaired ones. This suggests that the reproductive season influences the excretion patterns of endoparasite products and corticosterone metabolites and that affiliative interactions between pair partners may positively affect endoparasite burden during periods of elevated glucocorticoid levels. Being embedded in a pair bond may have a positive impact on individual immune system and parasite resistance.

Mobility cost of copulation is independent of female: Male size ratio in Anasa tristis

The fitness benefits of copulation are evident, but copulation can also incur costs to participating individuals. Many insects copulate for prolonged periods of time during which the female carries or drags the male. This behavior could result in decreased mobility, which in turn might influence the copulating pair's ability to escape from predators and to forage or thermoregulate. Here, I tested how copulation influences movement speed in the common squash bug (Anasa tristis) by measuring average movement speed of unpaired individuals and copulating pairs in an arena trial. Copulating pairs moved significantly slower but, surprisingly, the degree of size disparity between male and female did not influence movement speed. These results suggest that copulation incurs a mobility cost in this species, with potential consequences for survival, but that it is unlikely that mobility costs during copulation lead to selection for smaller male size.

Social and environmental factors modulate leucocyte profiles in free-living Greylag geese (Anser anser)

BackgroundBlood parameters such as haematocrit or leucocyte counts are indicators of immune status and health, which can be affected, in a complex way, by exogenous as well as endogenous factors. Additionally, social context is known to be among the most potent stressors in group living individuals, therefore potentially influencing haematological parameters. However, with few exceptions, this potential causal relationship received only moderate scientific attention.MethodsIn a free-living and individually marked population of the highly social and long-lived Greylag goose, Anser anser, we relate variation in haematocrit (HCT), heterophils to lymphocytes ratio (H/L) and blood leucocyte counts to the following factors: intrinsic (sex, age, raising condition, i.e. goose- or hand-raised), social (pair-bond status, pair-bond duration and parental experience) and environmental (biologically relevant periods, ambient temperature) factors. Blood samples were collected repeatedly from a total of 105 focal birds during three biologically relevant seasons (winter flock, mating season, summer).ResultsWe found significant relationships between haematological parameters and social as well as environmental factors. During the mating season, unpaired individuals had higher HCT compared to paired and family individuals and this pattern reversed in fall. Similarly, H/L ratio was positively related to pair-bond status in a seasonally dependent way, with highest values during mating and successful pairs had higher H/L ratio than unsuccessful ones. Also, absolute number of leucocytes tended to vary depending on raising condition in a seasonally dependent way.DiscussionHaematology bears a great potential in ecological and behavioural studies on wild vertebrates. In sum, we found that HTC, H/L ratio and absolute number of leucocytes are modulated by social factors and conclude that they may be considered valid indicators of individual stress load.

Song Functions in Nonduetting Gibbons: Evidence from Playback Experiments on Javan Gibbons (Hylobates moloch)

Territorial, pair-living primates usually perform long-distance calls as duets in which adult males and females coordinate their calls. Previous studies using playback experiments have shown that gibbon duets convey information about the status of the caller (location, familiarity, sex of the caller, and paired status) and gibbons use this information to respond to achieve several nonmutually exclusive functions, including intragroup contact, territorial defense, and pair-bond advertisement and strengthening. However, not all pair-living gibbons duet, and it is unclear whether the same results should be expected in nonduetting species. We conducted song playback experiments (N = 47 trials) to test hypotheses about song functions in nonduetting gibbons on two groups of wild Javan gibbons (Hylobates moloch) in the Gunung Halimun-Salak National Park, Indonesia. Javan gibbons initiated movement toward the speaker more quickly in response to songs broadcast in the center of the territory, stranger songs, and songs of unpaired individuals than to songs at the border, neighbor songs, and songs from paired individuals. These results suggest that Javan gibbons can localize songs, and that Javan gibbon songs transmit information about the identity and paired status of the caller. Our results imply that Javan gibbon solo songs are likely to function for territorial defense and pair-bond advertisement like duets in other primates.

Cost of reproduction: a comparison of survival rates of breeding and non‐breeding male ortolan buntings

The cost of reproduction is expected to influence survival or future reproduction. Most previous studies have assessed cost of reproduction in relation to natural and experimental variation in number of offspring produced. The ortolan bunting Emberiza hortulana is a passerine bird species with biparental care, and the Norwegian population of the species has an extraordinarily skewed sex ratio with only about half of the males attracting a female, and therefore provides a rare opportunity to compare survival of males that have paired and bred with that of non‐breeders (unpaired males), which have not paid a cost of reproduction. Results showed that survival rates of paired (65.0%) and unpaired (64.2%) males did not differ. However, when comparisons were restricted to paired males that definitely had nestlings, their survival rate (76.8%) was significantly higher than that of unpaired males, and the same was the case when comparisons were further restricted to paired males that had offspring recruiting to the population the next year (76.8% survived). Males breeding successfully are likely to be a biased subset of high quality males. In analyses of a subset of males that had bred successfully when young, there was no difference in survival of paired and unpaired individuals when these males were older. In conclusion, breeding male ortolan buntings did not appear to pay a cost of reproduction in terms of reduced survival to the next year compared to non‐breeding males. These results may be explained by non‐breeding males also incurring extra costs during the breeding season, and that costs of reproduction are not shared equally among sexes in the ortolan bunting and other bird species with biparental care.

A common genetic influence on human intensity ratings of sugars and high-potency sweeteners.

The perception of sweetness varies among individuals but the sources of this variation are not fully understood. Here, in a sample of 1,901 adolescent and young adults (53.8% female; 243 MZ and 452 DZ twin pairs, 511 unpaired individuals; mean age 16.2±2.8, range 12–26 years), we studied the variation in the perception of sweetness intensity of two monosaccharides and two high-potency sweeteners: glucose, fructose, neohesperidine dihydrochalcone (NHDC), and aspartame. Perceived intensity for all sweeteners decreased with age (2–5% per year) and increased with the history of otitis media (6–9%). Males rated aspartame slightly stronger than females (7%). We found similar heritabilities for sugars (glucose: h2=0.31, fructose: h2=0.34) and high-potency sweeteners (NHDC: h2=0.31, aspartame: h2=0.30); all were in the modest range. Multivariate modeling showed that a common genetic factor accounted for >75% of the genetic variance in the four sweeteners, suggesting that individual differences in perceived sweet intensity, which are partly due to genetic factors, may be attributed to a single set of genes. This study provided evidence of the shared genetic pathways between the perception of sugars and high-potency sweeteners.

Selection becomes visible: enforced sexual dimorphism caused by sexual selection in the weevilRhopalapion longirostre(Olivier 1807) (Coleoptera: Curculionoidea: Brentidae)

Extremely divergent traits between males and females are often the result of different requirements and behaviours of the sexes and will evolve relatively rapidly under selection forces. Sexual dimorphism in Rhopalapion longirostre is predominately manifested in the length and structure of the rostrum. To estimate how sexual selection shapes mating success in this weevil we compared paired and unpaired individuals collected from three populations in Austria. The mating process in this species is complex and lengthy. Statistical analyses based on detailed observations of their mating behaviour revealed that matched pairs show functional affinities in body size. Females and males with larger elytra, as well as males with large overall body size, are favoured mating partners, while males that are too small have no mating success. This arrangement ensures copulation and consequently successful egg deposition. For efficient egg channel boring into the flower buds of the host plant, Alcea rosea, the extremely long female rostrum is a crucial tool. Natural selection promotes longer rostra in females whereas sexual selection favours the shorter rostra in males. The major evolutionary forces, natural and sexual selection, enhance the sexual dimorphism in this species. © 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, 115, 38–47.

Perspectives of adults with epilepsy and their support persons on self-management support.

Social support is an important mechanism for improving self-management, although little is known about its role in epilepsy self-management. We examined the type of support provided to people with epilepsy and its influence on self-management. We conducted in-depth interviews with 22 people with epilepsy and 16 support persons, representing 14 pairs and 10 unpaired individuals. We analyzed the data using principles of grounded theory. Supporters, who were mainly parents and spouses, aided people with epilepsy in every dimension of self-management. Support for self-management occurred along a continuum from person with epilepsy-led management to support person-led management. Where the pairs fell on the continuum depended on developmental stage, relationship type, and relationship dynamics. Seizure control shaped individuals' experiences with self-management and support within each group. The self-management continuum provides a new aspect that can be integrated into existing models of self- and family management.

Criteria for determining breeding‐pair status of male mallards captured in decoy traps

ABSTRACTMethods for accurately determining pair status of male ducks during the breeding season are necessary for further understanding the roles of paired and unpaired males in waterfowl breeding populations. Previous studies assigned pair status based on behavioral observations of randomly captured and marked birds, but this method limits control over sample sizes of paired and unpaired individuals. We evaluated 8 criteria for determining breeding‐pair status (i.e., paired, unpaired) of male mallards (Anas platyrhynchos) based on scenarios of capture in decoy traps during late March–early April in Prairie‐Parkland Canada and central New York, USA. Of the 51 males we classified as paired across 3 study sites and years, we confirmed from repeated visual observations that 46 (90%) were indeed paired. All 36 males classified as unpaired were subsequently confirmed to be unpaired. The predicted overall probability of correctly assigning pair status to captured males was 93.7% (95% CI = 86.8–97.3%). These criteria provide an effective yet simple technique to identify pair status of male mallards captured in decoy traps and should enable more efficient use of time and logistical resources in studies requiring samples of paired and unpaired male ducks. © 2014 The Wildlife Society.

The Economics of Egg Trading: Mating Rate, Sperm Competition and Positive Frequency-Dependence

Egg trading—the alternating exchange of egg parcels during mating by simultaneous hermaphrodites—is one of the best-documented examples of reciprocity between non-relatives. By offering eggs only to partners who reciprocate, traders increase their reproductive success in the male role, but at a potential cost of delaying or reducing fertilisation of their own eggs. Although several authors have considered the evolutionary stability of egg trading once it has evolved, little attention has been paid to how egg trading can invade a population in the first place. We begin to tackle this problem by formally showing that egg trading is under positive frequency-dependent selection: once the proportion of traders in a population exceeds a certain threshold, egg trading will go to fixation. We show that if mate encounters occur frequently, then the cost of withholding eggs from unreciprocating partners is reduced, making it easier for egg trading to evolve. In contrast, the presence of opportunistic ‘streaking’, where unpaired individuals join mating pairs but contribute only sperm, makes it more difficult for egg trading to invade. This is because streakers weaken the link between the number of eggs an individual can offer and its male-role reproductive success.

Mate preference does not influence reproductive motivation and parental cooperation in female zebra finches

In socially monogamous species, low availability of sexually active unpaired individuals in the local population may constrain mate choice, resulting in mating with sub-optimal partners. Here we experimentally investigate whether female reproductive behaviour is different when paired with a preferred or a non-preferred male in the zebra finch (Taeniopygia guttata). First, we assessed female mating preferences using a four-way choice apparatus, then females were caged together with either their preferred or least-preferred male. Female reproductive motivation, assessed by the propensity of laying eggs within two weeks from pairing and clutch mass, did not differ between the two experimental groups. Females responded to mate removal by either increasing their care, so as to compensate for the lost care of their mate, or by significantly reducing incubation. This bimodal response was not explained by mate preference, nevertheless, we found that females with lower baseline (i.e., pre-manipulation) incubation effort were more likely to cease incubation during mate removal. Taken together, we found no evidence that female reproductive behaviour varies along with mate preference.

First report of egg predation by an unpaired Eurasian Coot, Fulica atra, L., 1758 (Aves: Gruiformes) on Black-winged Stilt, Himantopus himantopus, L., 1758 (Aves: Charadriiformes): one case from central Italy

The Eurasian Coot, Fulica atra, is a gregarious Palearctic rail that only rarely occurs singly. Even if resident birds can present territorial behaviour all through the year, most aggressions are developed during the breeding season, and the scientific literature has reported inter- and intraspecific attacks by Coot breeding pairs. Unpaired individuals do not usually show any territoriality and are often subjected to attacks by breeding pairs. It is, however, possible to observe unpaired Coots defending a territory before pairing, but the typical aggressive behaviour is developed after the beginning of nest building. Egg predation by Coots is reported as a rare phenomenon, exerted only by members of breeding couples. In this note, we report two predation cases exhibited by an unpaired individual against nests and eggs of Himantopus himantopus. We discard the hypothesis of competition for food between these two species and suggest that this peculiar behaviour could have been induced by endocrine hormonal secretions, regardless of whether the individual was paired or not.

The effect of pair bonding in Cabrera vole’s scent marking

The Cabrera vole (Microtus cabrerae) is a rare rodent living in patchy grassy areas of the Iberian Peninsula where unpaired individuals of both sexes use scent marking primarily to increase their mate-finding likelihood. Cabrera voles establish long-term pair bonds with opposite-sex conspecifics constituting a breeding pair, which is expected to reduce the efforts in searching for a new mate. Under such circumstances, scent marking as a strategy to increase mate-finding likelihood became useless. Accordingly, we hypothesise that pair bonded Cabrera voles suppress mate-finding scent marking to reduce energetic costs and predation risk. To test this hypothesis, we compared scent-marking behaviour towards a clean substrate, in both paired and non-paired voles. No differences were found in the scent marks’ type and the amount of marks placed by voles in both conditions. We also analysed the scent-marking behaviour of both sex pair bonded voles when exposed simultaneously to a clean substrate, a substrate pre-marked by males and a substrate pre-marked by females. We found no significant differences in scent-marks (urine-marked area and number of faecal boli) across the three types of substrate types. In accordance with our prediction, these results suggest that pair bonded Cabrera voles did not use scent marking for mate finding, thus providing further support to the existence of a monogamous mating strategy. Furthermore, our results fail to support the use of scent marking for territorial defence purposes.

Copulatory Behavior of Non-Migratory Whooping Cranes in Florida

Whooping Cranes (Grus americana) are a long-lived, monogamous avian species, yet little documentation of copulatory behavior and timing in relation to egg-laying has occurred in wild populations. We monitored 10 crane pairs in Florida before and during the 2010 breeding season to document copulation timing and pre- and post-copulatory behavior. Monitoring began 111 days before incubation initiation for the first nest of the season. Pairs were observed for 124.62 hrs ( = 76.30 min, range = 14–375 min) during 98 observation periods; 17 observation periods occurred on days with precipitation. Three copulations were observed, two by one established pair and another by unpaired individuals. The copulations by the established pair occurred 9 and 18 days before incubation began. The third was an extra-pair copulation, which occurred between a paired female and a lone male, the first documented for the species. No copulations were observed on days with precipitation. We examined flock monitoring accounts from 1999 through 2009 in this non-migratory population; 21 observations of copulations revealed Whooping Cranes copulated up to 62 days before incubation began and between 0510–1345 hrs EST. Our data suggest copulation occurs between early morning and early afternoon and does not appear to be associated with precipitation.