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Effects of mate separation in female and social isolation in male free-living Greylag geese on behavioural and physiological measures
Abstract
The presence of a social partner may significantly contribute to coping with stressful events, whereas dyadic separation generally increases glucocorticoid levels and, thereby, might also affect immune function and health. To study the covariation between social factors, immuno-reactive corticosterone metabolites, haematology and parasite product excretion patterns in a free-living, long-term monogamous bird, we separated pair mates in Greylag geese (Anser anser). We isolated the males of eight pairs for 48 hours to examine behavioural, adrenocortical, haematological and parasitological responses to mate removal in the female partners, and to social isolation in the males. Females showed no elevated levels of corticosterone metabolites in their droppings, but their haematocrit decreased during mate removal, whereas leucocyte number and heterophil/lymphocyte (H/L) ratio remained unchanged. In contrast, the socially isolated males excreted significantly elevated levels of corticosterone metabolites compared to baseline and showed a decrease in haematocrit as well as elevated leucocyte number and H/L ratio. In both sexes, the excretion of coccidian oocysts increased within 48 hours of the start of the separation, remained high one week after separation, and returned to baseline four weeks later. Described effects were generally more pronounced in males than in females. Our results suggest relatively swift potential health effects of mate loss and social isolation in an unfamiliar confinement in free-living geese.
... Therefore, knowledge on such interactions is crucial (Baos et al., 2006;Fair and Ricklefs, 2002;Munns, 2006). In social species, such as geese, social isolation is an ecologically relevant and potent stressor (Hawkley et al., 2012;Kralj-Fišer et al., 2013;Ludwig et al., 2017), which can be useful to study such interactions. Living in a structured group is a key element of social species and a proper social embedding is crucial for an individual's survival and well-being (seeHawkley et al., 2012). ...
... Irrespective of mine-exposure, goslings had on average two-timeshigher blood corticosterone concentrations after isolation. Our study thereby adds to the known effects of social isolation on glucocorticoids in social mammals (reviewed byHawkley et al., 2012) and especially to the less extensive literature in social bird species (but seeApfelbeck and Raess, 2008;Banerjee and Adkins-Regan, 2011;Ludwig et al., 2017;Perez et al., 2012;Remage-Healey et al., 2003). In free-living adult greylag geese (Anser anser), socially isolated males excreted increased levels of corticosterone metabolites compared to baseline, while their mates, who were not taken out of their familiar environment, did not show increased levels of corticosterone (Ludwig et al., 2017). ...
... Our study thereby adds to the known effects of social isolation on glucocorticoids in social mammals (reviewed byHawkley et al., 2012) and especially to the less extensive literature in social bird species (but seeApfelbeck and Raess, 2008;Banerjee and Adkins-Regan, 2011;Ludwig et al., 2017;Perez et al., 2012;Remage-Healey et al., 2003). In free-living adult greylag geese (Anser anser), socially isolated males excreted increased levels of corticosterone metabolites compared to baseline, while their mates, who were not taken out of their familiar environment, did not show increased levels of corticosterone (Ludwig et al., 2017). Circulating corticosterone increased in one-year-old starlings (Sturnus vulgaris) when they were visually isolated from their social group for approximately 20 h (Apfelbeck and Raess, 2008). ...
In many areas around the Arctic remains and spoil heaps of old mines can be found, which have been abandoned after their heydays. Runoff from tailings of these abandoned mines can directly contaminate the local environment with elevated concentrations of trace metals. Few studies have investigated the possible negative effects of contaminants on Arctic terrestrial animals that use these areas. Trace metals can accumulate in animals and this accumulation has been linked to negative effects on fitness. Both, the hypothalamus-pituitary-adrenal (HPA) axis and/or the immune system have been named as possible underlying causes for these observations. Free-living animals are often exposed to multiple stressors simultaneously, however, and this is often not considered in studies on the effects of contaminants on animal physiology. Here, we performed a study on Spitsbergen (Svalbard) taking both potential effects of trace metal contamination and social stress into account. We investigated experimentally effects of exposure to contaminants from a historic coal mine area on plasma corticosterone levels and on four innate immune parameters (haemolysis, haemagglutination, haptoglobin-like activity and nitric oxide) before and after social isolation in human-raised barnacle goslings (Branta leucopsis). Baseline corticosterone and immune parameters were not affected by mine-exposure. After social isolation, mine goslings tended to show decreased haemagglutination in comparison with control goslings, but we detected no difference in the other measures. Social isolation increased corticosterone and decreased haptoglobin-like activity in all goslings. Immunology and corticosterone levels of barnacle goslings thus seem unaffected, at least on the short term, by Arctic coal mining contamination.
... Ducks, geese, quail welfare on farm and Ross, 1982 for ducks; Ludwig et al., 2017 for Greylag geese). These welfare consequences are not listed under TOR-2 but are relevant for consideration in addition to group stress, as they are all affected by the access to conspecifics. ...
... Regarding the impact of group size on the welfare of ducks, geese and quail, there is very limited scientific evidence. Studies on greylag geese (Ludwig et al., 2017) and quail have shown that social isolation influences animal health and welfare, depending on the general sociality of the species (see Section 3.5.3). Studies on the impact of maximum group size have not been found. ...
This Scientific Opinion concerns the welfare of Domestic ducks (Anas platyrhynchos domesticus), Muscovy ducks (Cairina moschata domesticus) and their hybrids (Mule ducks), Domestic geese (Anser anser f. domesticus) and Japanese quail (Coturnix japonica) in relation to the rearing of breeders, birds for meat, Muscovy and Mule ducks and Domestic geese for foie gras and layer Japanese quail for egg production. The most common husbandry systems (HSs) in the European Union are described for each animal species and category. The following welfare consequences are described and assessed for each species: restriction of movement, injuries (bone lesions including fractures and dislocations, soft tissue lesions and integument damage and locomotory disorders including lameness), group stress, inability to perform comfort behaviour, inability to perform exploratory or foraging behaviour and inability to express maternal behaviour (related to prelaying and nesting behaviours). Animal-based measures relevant for the assessment of these welfare consequences were identified and described. The relevant hazards leading to the welfare consequences in the different HSs were identified. Specific factors such as space allowance (including minimum enclosure area and height) per bird, group size, floor quality, characteristics of nesting facilities and enrichment provided (including access to water to fulfil biological needs) were assessed in relation to the welfare consequences and, recommendations on how to prevent the welfare consequences were provided in a quantitative or qualitative way.
... This is supported by a study in carrion crows, showing coccidian oocysts, but not nematode eggs to significantly increase in the first week after a major stressor (Spreafico et al. 2012). In graylag geese, excretion of coccidian oocysts, but not nematode eggs are significantly increased in the first week after social isolation (Ludwig et al. 2017). ...
In group-living animals, the social environment is thought to affect the probability of parasite transmission. Here, I investigate relationships between social behaviour and gastrointestinal parasite product excretion in the carrion crow (Corvus corone). Individuals from a population of non-cooperatively breeding carrion crows excreted less samples containing coccidian oocysts when kept in larger groups (8 or 9 individuals) compared to those individuals kept in smaller groups (2 or 3 individuals). Lower-ranking individuals excreted more samples containing parasite oocysts compared to higher-ranking individuals. The strength of affiliative relationships and number of related individuals in the group did not relate to the proportion of droppings containing coccidian oocysts. The present results confirm an association between social environment and parasite excretion patterns in carrion crows, but the patterns described in the present study differ from previously published data derived from a group of cooperatively breeding crows. This illustrates that differences between the social systems of carrion crows might result in different associations between the social environment and parasite product excretion patterns.
Significance statement
One major cost of group living is increased susceptibility to parasites. Not all individuals are affected by this in the same way. A better understanding of the relationship between social behaviour and parasite burden can help to better understand evolution of group living. I investigate associations between dominance rank, affiliative relationships, group size, and gastrointestinal parasite product excretion in a group of captive carrion crows. Lower-ranking individuals excreted more samples containing parasite oocysts compared to higher-ranking individuals, confirming an association between social relationships and parasite excretion patterns.
... It is known that the erythrocytes (red blood cells) or birds are nucleated and larger than cells of mammals. The heterophiles have similar function to the neutrophils in mammals and are the main phagocytic cells involved in the inflammatory response (Capitelli & Crosta, 2013), besides being considered stress markers in some studies with birds, and there is also a correlation value between lymphocytes and heterophile known as an indicator of chronic stress in birds (Leclerc et al., 2017;Ludwig et al., 2017). Whereas the thrombocytes have functions related to hemostasis and the thromboplastin production, but also perform phagocytic function. ...
Domestic geese are birds of zootechnical interest commonly created for ornamentation and guard in farms but are also useful for biomedical research, once they supply blood as a byproduct for laboratory analysis. The study aimed to contribute to the completion of health data available on these animals to trace a hematological profile of domestic geese that supply blood for research and provide data on the influence of periodic collections to the health of these animals. Ten Chinese geese (Anser domesticus), white and males, were kept in a research center installation. Four blood samples were performed weekly after the 1st collection, the sample with greater volume was sent to the laboratories of the Evandro Chagas Institute to be used in the arbovirus tests. The hematological evaluations observed values of packed cell volume (PCV), total number of erythrocytes (Hm), total number of leukocytes (Lc) and differential leukocyte count and the number of thrombocytes (Tb). All the animals were weighed and correlation of volume of blood collected from the animal’s weight was performed. No differences were found among the means obtained in the hematological values of the 1st collection and the subsequent collections demonstrating that the periodic collection in geese, when performed in obedience to the correlation between animal’s weight and blood volume, does not cause significant alterations in the animal’s hematological profile. The results of the hematological profile obtained in this study will add to the biological data of species available allowing a better health assessment of these animals in the creation of environments and in animal research facilities.
... Whereas numerous studies have considered the positive (e.g. Scheiber et al. 2009;Frigerio et al. 2005;Young et al. 2014;Ludwig et al. 2017) or negative (e.g. Goymann and Wingfield 2004;Ostner et al. 2008) relationships between social environments and individual GC levels in groupliving species, few have concurrently investigated the joint effect of socially aggressive and socially tolerant environments on the stress axis of free-living vertebrates (Dantzer et al. 2017). ...
Social interactions among conspecifics can have marked effects on individual physiology, especially through their modulation of the stress axis by affecting the production of adrenal glucocorticoids (GCs). Previous research has focused on how individual GC levels may be influenced by social status, but few studies have considered how the balance between positive (e.g. cooperation) and negative (e.g. competition) social interactions shape individual GC levels. A lack of association between individual GC levels and social factors may be confounded by opposite effects of social competition on the one hand and social cooperation on the other. We tested for these effects in the Columbian ground squirrel (Urocitellus columbianus), a colonial rodent. During the breeding season, females are exposed to territorial unrelated neighbors and to territorial, but more tolerant, close kin. On one hand, territoriality and competition for resources led us to predict a positive association between local colony density and female GC levels. On the other, higher tolerance of philopatric kin females and known fitness benefits led us to predict a negative association between kin numbers and female GC levels. We compared levels of fecal cortisol metabolites (FCMs) in females at two different spatial scales during lactation: local (a female’s core territory during lactation, 30-m radius about her nest burrow) and colony-wide. At the local scale, female FCM levels were neither related to colony density nor to the number of co-breeding female kin, but FCM levels increased with age. At the colony scale, female FCM levels varied in a quadratic fashion with female kin numbers. FCM levels decreased by 15% from 0 to 1 co-breeding kin present and increased with > 1 kin present. Among females that had only one co-breeding kin present, daughters (and littermate sisters and mothers, but not significantly) led to a 14% reduction in FCM levels compared with females that had no kin. Our results reject the idea that local colony density is associated with increased GC levels this species, but indicate subtle (positive and negative) effects of kin on individual GC secretion. They further call into question the importance of the nature of social relationships in modulating the stress experienced by individuals.
Significance statement
Few studies have tested how the balance between positive (e.g. cooperation) and negative (e.g. competition) social interactions shapes individual stress and glucocorticoid (GC) levels in group-living animals. In colonial Columbian ground squirrels, breeding females are exposed to territorial neighbors and to more tolerant close kin. We show that kin numbers have subtle (positive and negative) effects on female GC levels. Compared with breeding females with no kin, female GC levels decrease by 15% with the presence of a single co-breeding close relative, but increase with the presence of more than one co-breeding related female. Among females that have only one co-breeding kin, the presence of daughters (and littermate sisters and mothers, but not significantly) leads to a 14% reduction in female GC levels. Our results highlight how GC levels may be influenced by the specific nature of social relationships in group-living animals.
... The absence of such social support (i.e. social isolation) can, in turn, have negative effects on fitness; in greylag geese, solitary confinement or mate-loss affects immuno-reactive corticosterone metabolites, percentage of red blood cells and intestinal parasite loads(Ludwig, Kapetanopoulos, Kotrschal, & Wascher, 2017).Integrating the individual's state, the response of the group and following it back to the individual might generate new insights on how social groups respond to environmental stressors. Observing individuals under environmental pressures that push their physiological limits, such as food or water shortages, high temperatures or increased predation, can provide an opportunity to study feedbacks and behavioural drivers. ...
1.The social decisions that individuals make, in terms of where to move, who to interact with and how frequently, scale up to generate social structure. Such structure has profound consequences: individuals each have a unique social environment, social interactions can amplify or dampen individual differences at the population level, and population-level ecological and evolutionary processes can be governed by higher-level ‘emergent properties’ of animal societies.2.Here we review how explicitly accounting for social structure in animal populations has generated new hypotheses and has revised existing predictions in ecology and evolution. That is, we synthesize the insights gained by applying ‘network-thinking’ rather than the utility of applying social network analysis as a methodological tool. 3.We start with what has been learned about the generative mechanisms that underpin social structure. We then outline the major implications that social structure has been found to have on population processes, on how selection operates and organisms can evolve, and on co-evolutionary dynamics between social structure and population processes. Finally, we highlight areas for which there is clear evidence that accounting for social structure will refine current thinking, but where examples remain scarce.4.Applying ‘network thinking’ in biology presents not only new challenges, but also many opportunities to advance different areas of research. Addressing the question of how social structure changes the biological relationships linking individuals to populations, and populations to processes, is revealing commonalities across scientific disciplines. In doing so, animal social networks can bridge otherwise disparate research topics and, in the future, we hope will allow for more unified theories in biology.
... The social isolation in social species like geese, is an ecologically relevant and acts as a stressor [106]. Stress is not only immunosuppressive, but can also have no effect or can even be immunoenhancing. ...
... The social isolation in social species like geese, is an ecologically relevant and acts as a stressor [106]. Stress is not only immunosuppressive, but can also have no effect or can even be immunoenhancing. ...
... The social isolation in social species like geese, is an ecologically relevant and acts as a stressor [106]. Stress is not only immunosuppressive, but can also have no effect or can even be immunoenhancing. ...
... Haematocrit (HCT), which is the relative volume of red blood cells compared to the total blood volume, is an indicator of an animal's physical condition (Hõrak et al., 1998;Fair et al., 2007) and is known to decrease in response to stressful conditions (Dickens et al., 2009;Ludwig et al., 2017). However, HCT also varies with sex, age, reproductive status, as well as geographic distribution (Dawson and Bortolotti, 1997;Fair et al., 2007) and therefore it has to be mentioned that haematological parameters as indicators of stress, physical condition and health are controversial (O'Brien et al., 2001;Romero, 2004;Davis et al., 2008;Kaliński et al., 2011;Lill et al., 2013;Minias, 2015). ...
In precocial species, large brood sizes are usually considered as beneficial and individuals in larger broods grow faster and are more dominant compared to individuals in small broods. However, little is known whether family size also beneficially affects the offspring's physiology. In the present study, we investigated whether leucocyte profiles in fledgling Greylag Geese (Anser anser) are affected by (1) family size, (2) individual characteristics, i.e. age, body condition or sex, or (3) characteristics of the parents, i.e. previous reproductive success. From spring 2013 to autumn 2015, we collected blood samples from 100 juvenile Greylag Geese from 20 different pairs. From these samples we determined the absolute leucocyte number, an individual's differential blood cells count and an individual's haematocrit (HCT). The number of fledglings in a family and therefore the number of siblings a focal individual had, was positively related to the percentage of basophils, negatively to the heterophils/lymphocytes ratio (H/L), and tended to be negatively related to the percentage of monocytes and eosinophils in a sample. H/L ratio was negatively related to age in days and tended to be negatively related to body condition, whereas the percentage of basophils tended to be positively related to it. Absolute leucocyte number did not differ between individuals depending on family size. However, composition of different leucocyte types (basophils, eosinophils, H/L ratio) was modulated mostly by the social environment (family size) and not by the characteristics of the individual or the parents. In conclusion, even though we did not find clear evidence of a positive health effect, i.e. a better immune system, in fledgling Greylag Geese of large versus small families, our results suggest that family size modulates different components of the immune system hinting at its stress-reducing effect.
Updated tables, figures and references of Palme, 2019,
and the respective supplements (Date: 3rd July 2023)
The Anseriforme order of birds is composed of at least 180 waterfowl species within three families. Hematology is a rapid, inexpensive, and relatively minimally invasive method to evaluate some aspects of health in these species. The erythron is assessed by the same means as other birds, using total red blood cell (RBC) count, PCV, hemoglobin concentration, mean cell volume, mean cell hemoglobin concentration, and evaluation of RBC morphology. The leukon is assessed by the same means as other birds and includes a total white blood cell (WBC) count, differential WBC counts, and morphologic evaluation. There is a paucity of information regarding thrombocytes and coagulation in Anseriformes. Thrombocyte clumping is typically interpreted to indicate an adequate thrombon mass. Several biologic factors influence reference intervals in Anseriformes and these must be considered when designing or reviewing a reference interval study. Very little work has been done to characterize normal bone marrow in Anseriformes.
The social decisions that individuals make—who to interact with and how frequently—give rise to social structure. The resulting social structure then determines how individuals interact with their surroundings—resources and risks, pathogens and predators, competitors and cooperators.
However, despite intensive research on (a) how individuals make social decisions and (b) how social structure shapes social processes (e.g. cooperation, competition and conflict), there are still few studies linking these two perspectives. These perspectives represent two halves of a feedback loop: individual behaviour scales up to define the social environment, and this environment, in turn, feeds back by shaping the selective agents that drive individual behaviour.
We first review well‐established research areas that have captured both elements of this feedback loop—host–pathogen dynamics and cultural transmission. We then highlight areas where social structure is well studied but the two perspectives remain largely disconnected. Finally, we synthesise existing research on 14 distinct research topics to identify new prospects where the interplay between social structure and social processes are likely to be important but remain largely unexplored.
Our review shows that the inherent links between individuals’ traits, their social decisions, social structure and social evolution, warrant more consideration. By mapping the existing and missing connections among many research areas, our review highlights where explicitly considering social structure and the individual‐to‐society feedbacks can reveal new dimensions to old questions in ecology and evolution.
Mate separation has been shown to mediate changes in physiological and behavioral processes via activation of the hypothalamo‐pituitary‐adrenal (HPA) axis in both mammalian and avian species. In order to elucidate the neural mechanisms associated with changes in the HPA axis in response to social stress, we investigated the effects of mate pair separation on circulating corticosterone concentrations as well as gene expression levels of mineralocorticoid receptor (MR), glucocorticoid receptor (GR), and corticotropin releasing hormone (CRH) in the hypothalamus and hippocampus of both male and female zebra finches, a species that forms strong pair bonds. Zebra finches (Taeniopygia guttata) were housed three to a cage (a mated pair plus a stimulus female), and were assigned to one of three new housing treatment groups: (1) male or female removed from their respective mate and placed in a cage with a new opposite sex conspecific and stimulus female (2) male or female that remained with their mate, but a new stimulus female was introduced, or (3) the subjects were handled but not separated from their mate or the stimulus female. After 48 hours in the new housing condition, we observed significant increases in plasma corticosterone concentrations in response to both mate pair and stimulus female separation. No significant differences in MR, GR, or CRH mRNA expression in the hypothalamus were observed in response to any treatment for both males and females. Females exhibited a significant up regulation in hippocampal MR, but not GR mRNA, whereas males exhibited a significant down regulation of both hippocampal MR and GR mRNA in response to mate pair separation. Thus, the hippocampus appears to play a key role in regulating sex specific responses to social stressors. This article is protected by copyright. All rights reserved.
We measured corticosterone in plasma collected from free-living Adélie Penguins (Pygoscelis adeliae) and made blood smears to count the ratio of heterophils to lymphocytes (H/L). Our objective was to categorize how these two measures of stress vary with potential stressors in the birds' environment. In penguins that were repeatedly sampled from three to eight times, repeated handling did not affect corticosterone levels or H/L, but there were significant differences among individuals. Nesting stage did not affect corticosterone level, but H/L was significantly lower during the chick stage than in the courting or incubation stages. Sex and handling times of less than 5 min had no effect on either corticosterone or H/L. In birds that had fasted up to 40 days during the courtship and early incubation stages, there was no increase in corticosterone or H/L with length of fasting, but in birds that had fasted more than 50 days, corticosterone levels increased. Birds with obvious injuries had significantly higher H/L than birds that had recently engaged in fights or those caring for chicks, but corticosterone levels did not differ in these groups. In free-living birds, H/L ratios provide a measure of stress that may be more useful than a single measure of plasma corticosterone in assessing response to chronic stressors like injury or crowded conditions in the breeding colony.
Background
Blood 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.
Methods
In 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).
Results
We 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.
Discussion
Haematology 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.
We studied effects of mate removal on nesting and hatching success, incubation behavior, body mass, and post-hatch dispersal distance of female Ross' (Chen rossii) and Lesser Snow Geese (C. caerulescens caerulescens) at Karrak Lake. N.W.T., Canada. Male ge and widowed and paired control females were monitored through post-hatch dispersal. Nesting and hatching success did not differ between species or treatments (widowed vs paired) and averaged 77.5 ± 3.8% and 64.0 ± 3.6% (±SE), respectively. Paired females spent more time with their bills tucked (23.7 ± 3.3% vs 9.1 ± 4.0%) and less time alert (8.6 ± 2.9% vs 22.9 ± 3.5%) while on nests than did widowed females. Snow widowed females (31.1 ± 4.7%) and Ross' widowed females (20.6 ± 6.0%) generally spent more time each day in head-up alert than did Snow paired females (7.1 ± 3.8%). Snow paired maleS (11.8 ± 3.8%), Ross' paired females (9.4 ± 3.6%), and Ross' paired males (7.9 ± 3.6%). Body mass of paired and widowed female Ross' Geese did not differ at hatch or at time of post-hatch recapture; however, mean distance recaptured from the breeding colony was greater for paired (50.9 ± 6.1 km) than for widowed females (27.3 ± 6.6 km). Total mass gain (276 ± 19 g) and rate of mass gain (8.4 ± 0.5 g/day), from hatch until post-hatch recapture (33.1 ± 1.2 days), were similar for widowed and paired female Ross' Geese. Male removal experiments in monogamous, precocial species generally have produced few effects on female nesting success or incubation behavior. We suggest that male parental care in arctic-nesting geese is more critical during laying and the post-hatch period than during incubation.
For birds maintaining long-term monogamous relationships, mate loss might be expected to reduce fitness, either through reduced
survival or reduced future reproductive investment. We used harvest of male brant during regular sport hunting seasons as
an experimental removal to examine effects of mate loss on fitness of female black brant (Branta bernicla nigricans; hereafter brant). We used the Barker model in program MARK to examine effects of mate loss on annual survival, reporting
rate, and permanent emigration. Survival rates decreased from 0.847 ± 0.004 for females who did not lose their mates to 0.690
± 0.072 for birds who lost mates. Seber ring reporting rate for females that lost their mates were 2 times higher than those
that did not lose mates, 0.12 ± 0.086 and 0.06 ± 0.006, respectively, indicating that mate loss increased vulnerability to
harvest and possibly other forms of predation. We found little support for effects of mate loss on fidelity to breeding site
and consequently on breeding. Our results indicate substantial fitness costs to females associated with mate loss, but that
females who survived and were able to form new pair bonds may have been higher quality than the average female in the population.
Little is known about whether chewing lice (Insecta: Phthiraptera) suppress or activate immunity in birds. Here, relationships between lice (Quadraceps punctatus, Saemundsonnia lari and Austromenopon and immune parameters were evaluated in Ring-billed Gull (Larus delawarensis) chicks. Eosinophils made up greater proportions of leukocytes in chicks with more lice (partial r = 0.64, P < 0.001), suggesting louse-induced immunoactivation via either eosinophil production or redistribution to peripheral blood. However, there were no significant relationships between lice and other immune parameters (proportion heterophils, proportion lymphocytes, heterophil: lymphocyte ratio, response to injection with phytohaemagglutinin). Collectively, results suggest only minor immune responses to lice, but experimental manipulations of louse infestations are needed to better quantify these responses and evaluate their potential consequences for fitness.
The monthly occurrence of endoparasites in feral Greylag Geese Anser anser near
Stuttgart, southwest Germany was studied in 2007 and 2008. Seven genera of
parasites were found in the faecal samples. Nematode ova were most prevalent,
followed by protozoan oocysts, whereas only a few cestode ova were recovered. The
level of parasite infestation varied regionally and seasonally. More birds were found
to have parasites in winter than in summer, which was reflected by a negative
correlation between mean monthly temperature and the percentage of geese with
parasites. Parasite loads were low and there was no measurable negative effect of
parasites on the body condition of the geese.
We compared the daily plasma corticosterone (B) profiles in captive and free-living White-throated Sparrows (Zonotrichia albicollis) and White-crowned Sparrows (Z. leucophrys) during their non-breeding period. Neither sparrow species exhibited signif- icant die1 rhythms in the levels of corticosterone in captivity or under natural conditions, although the variations were suggestive of a rhythm. In each species, secretory profiles differed significantly between captive and free-living birds with mean B levels being 2-3 times higher in captive birds than in free-living individuals, despite the fact that captives had been "acclimated" for 35 days prior to sampling. Furthermore, mean B levels were two to four times higher in White-throated Sparrows under captive and free-living conditions than in White-crowned Sparrows under the same conditions. Our results indicate the need to use caution when (1) extrapolatin g such data obtained from captive individuals to those under natural conditions and (2) extrapolating data regarding B from one species to another. Received 28 July 1994, accepted I Dec. 1994. Environmental stimuli may affect the concentrations and secretory pat- terns of hormones, such as the "stress-related" corticosteroid hormones, which can dictate physiological changes in organisms. In birds, the prin- cipal corticosteroid hormone is corticosterone (hereafter "B") (Assen- macher 1973). Perception of stressful stimuli markedly enhances the rate of B secretion through the actions of adrenal cortical stimulating hormone (ACTH), resulting in increased levels of B in the blood (Siegel 1971, 1980). In birds, this cause-effect relationship has been shown to occur in
The convict cichlid Amatitlania nigrofasciata is a monogamous, biparental teleost species. Convict cichlids form pairs to provide parental care and share in territory defence. In order for pairs to be successful there must be coordination of behaviour between the sexes. Although pair dynamics have been studied in the laboratory, few field experiments have investigated male and female responses to mate removal. We examined how convict cichlids modulate their parental defence behaviour in response to mate removal at Lomas Barbudal Biological Reserve, Costa Rica. We presented convict cichlid pairs with a conspecific intruder and observed the parental defence behaviour of both individuals. One member of the pair was then removed and the remaining individual was presented with the intruder. Both males and females significantly increased aggression towards the intruder after the removal of the mate; however, males were able to fully compensate for the loss of the female, whereas females were not. These results suggest that both male and female convict cichlids may modulate their behaviour in response to changing stimuli.
Factors affecting infection of birds by haemoparasites
have received much attention during the
last decade, since blood parasites can affect fitness
components (Merino et al. 2000), community
structure (Minchella & Scott 1991, Hudson &
Greenman 1998) and evolution (Hamilton & Zuk
1982, Howard 1991). Infection can be influenced
by three factors (a) presence of the appropriate
vector (Bennett et al. 1992, Little & Earlé 1995,
Piersma 1997, Figuerola 1999, Sol et al. 2000,
Jovani et al. 2001), (b) presence of the right hostparasite
assemblage (Earlé & Underhill 1993, Little&
Earlé 1994, Stewart et al. 1997, Blanco et al.
1998, Jones & Shellam 1999) since avian haematozoa
are specific to host families or subfamilies
(Ricklefs 1992), and (c) immunological capabilities
of the host (Ricklefs 1992, Figuerola et al.
1996, Tella et al. 1999). Here we compare the
competence of the immune system of European
Storm-petrels Hydrobates pelagicus with that of
syntopically breeding Mediterranean Yellowlegged
Gulls Larus argentatus michahellis
Haematocrit and buffy coat, the proportion of blood volume taken by red and white blood cells respectively, are commonly used as health indicators in humans. We investigated haematocrit and buffy coat in relation to the development of breeding plumage (proportion of feathers replaced), mass and capture date in dunlins Calidris alpina prior to spring migration. In particular, we tested the hypothesis that dunlins with relatively more advanced breeding plumage were in better condition. When comparing between capture sessions, buffy coat decreased over time. Within capture sessions buffy coat was not correlated with development of breeding plumage, but in each capture session birds with high mass had lower buffy coat, suggesting that birds with high mass were in better health. When comparing between capture sessions, haematocrit increased before departure, which is presumably an adaptation to migration because it increases oxygen transport capacity. Within capture sessions haematocrit was positively correlated with breeding plumage score, but neither was correlated with mass. However, the haematocrit of a bird with a given plumage score was independent of the date on which it attained that score, and thus there was no evidence that birds that started moult earlier and had a more advanced breeding plumage were in better condition.
We measured corticosterone in plasma collected from free-living AdClie Pen- guins (Pygoscelis adeliae) and made blood smears to count the ratio of heterophils to lym- phocytes (Ha). Our objective was to categorize how these two measures of stress vary with potential stressors in the birds' environment. In penguins that were repeatedly sampled from three to eight times, repeated handling did not affect corticosterone levels or HIL, but there were significant differences among individuals. Nesting stage did not affect corticosterone level, but H/L was significantly lower during the chick stage than in the courting or incu- bation stages. Sex and handling times of less than 5 min had no effect on either corticoste- rone or Ha. In birds that had fasted up to 40 days during the courtship and early incubation stages, there was no increase in corticosterone or H/L with length of fasting, but in birds that had fasted more than 50 days, corticosterone levels increased. Birds with obvious in- juries had significantly higher H/L than birds that had recently engaged in fights or those caring for chicks, but corticosterone levels did not differ in these groups. In free-living birds, HL ratios provide a measure of stress that may be more useful than a single measure of plasma corticosterone in assessing response to chronic stressors like injury or crowded conditions in the breeding colony.
Animals are hand-raised in a variety of contexts, including experimental research. This has been criticized frequently as producing animals with species-untypical behaviour. Here we compare life histories of 330 hand-raised and 631 gooseraised Greylag geese from a free-flying flock to determine whether hand-raising affected life history, reproductive variables and behaviour. We found little differences in life histories (e.g. male age, age at pair bond) or reproductive variables (e.g. number of eggs, egg weight, number of young hatched and fledged) of hand-raised and goose-raised geese. However, hand-raised females had lower life expectancies than goose-raised ones, mainly due to predation during breeding. Hand-raised geese were stressed significantly less during social, handling and predator stress, were attacked less by conspecifics and were less vigilant than goose-raised geese. We conclude that hand-raising resulted in geese with species-typical life histories but reduced stress responses. This makes hand-raised geese cooperative partners for research, but also more vulnerable when exposed to predators. Keywords: hand-raising; greylag goose;
Anser anser
; life-history; reproductive success; stress
K.T. 2002: Effects of mate removal on the fecundity of common eider Somateria mollissima females. -Wildl. Biol. 8: 161-168. Behavioural observations, measurements of male and female reproductive success, and DNA microsatellite loci were used to investigate parentage of com-mon eider Somateria mollissima clutches and productivity of widowed females in Finland. In an experimental study simulating spring harvest of male eiders, a total of 20 males were shot while attending 16 females (four males after remat-ings, 16 initial males) during the pre-laying and laying period in 1994. Of the 16 widowed females, 11 nested and five did not. Mean clutch size of breed-ing widows (4.55) did not differ from that of control females in the same year (4.47; N = 32). However, the hatching success of widows was significantly low-er than that of control females (53 vs 81%) because of a greater proportion of addled eggs and dead embryos (38% vs 11%). Male removal also appeared to change male and female behaviours resulting in higher incidence of intra-spe-cific brood parasitism and mate replacement. Occurrence of foreign eggs averaged 9.5% during the treatment year but was not observed during a year without disturbance during mating and egg laying (1997). Behaviours of wid-owed females related to remating attempts varied from active seeking of new mates to total rejection of courting males. Rematings did not lead to full clutch fertilisation among widowed females. Neither did we observe evidence of im-migration of new males into the hunting area to court the widows. Male removal clearly lowered the fecundity of eider females, reducing nesting success by 35% of long-term averages. The potential for remating appears to be reduced by the female-biased sex ratio caused by simulated male-only harvest.
The validity of the haematocrit or packed cell volume as an indicator of condition in wild birds has recently been questioned. We reviewed over 300 published papers on haematocrit values for wild birds. These studies show that changes in haematocrit could be caused by a number of different natural factors that include age, sex, geographical elevation, energy expenditure, parasitism, nutrition and genetics. Haematocrit also increased with age from hatching, due to increased erythropoiesis, so that adult birds generally have greater haematocrit values than nestlings or juveniles. Haematocrit values were either independent of elevation or increased with elevation. A meta-analysis of 36 studies showed no difference in haematocrit between the sexes. Relationships between haematocrit value and both energy expenditure and parasitic infection vary between studies. In temperate climates, haematocrit tended to be higher in winter than in summer, which may be due to dehydration or increased oxygen demand caused by thermogenesis, moult or acquisition of reproductive status. Our review indicates that the use of haematocrit as a sole indicator of condition or health could lead to incorrect conclusions if natural factors that can affect haematocrit are not taken into consideration.
Although greylag geese Anser anser establish long-term monogamous pairbonds, some of the existing pairs do split up (divorce) and new pairs are formed during the annual spring mating period. In this study, male greylag geese which were involved in the challenge of an existing pairbond (challenged males and challengers) were regarded as ‘natural experimental’ groups and compared with males in stable pairbonds (unchallenged males and male-paired males, a common male strategy when the availability of females is low). In total, 37 males were investigated. The analysis included a description of the seasonal patterns of hormone levels, aggression and courtship. We tested whether hormone levels correlated with aggressive and courtship behaviours. Finally, we compared hormonal and behavioural patterns amongst the four groups. Immunoreactive testosterone (T) and corticosterone (B) equivalents were measured in faecal samples. Individual hormone levels were correlated with frequencies of agonistic male-male interactions and with frequencies of male-female courtship. During early mating and pre-laying phases, T was at its seasonal maximum, which may have masked hormone-behaviour correlations. During egg-laying, at the onset of seasonally decreased T, agonistic male-male interactions and the frequencies of courtship behaviour were significantly correlated with T. Unchallenged males had higher rates of agonistic interactions than any other males. However, unchallenged and challenged males tended to excrete T at higher levels than challengers. The high rates of being attacked and elevated levels of faecal B were indicative of the social conflict experienced by challengers. No hormonal differences were observed between heterosexually paired males and male-paired males. In summary, pairbond status and situations of social conflict had a modulating effect on T and B; however, in this study, the two hormones seem to be affected independently of one another.
The effects of an endurance flight on the haematocrit, the percentage of packed red blood cells per blood volume, were examined within the framework of six possible factors explaining possible changes in the haematocrit. Two approaches were adopted: (1) the haematocrit was studied in four species of passerine birds which landed on an Italian island after having crossed the Mediterranean Sea on their spring migration in a non-stop flight; (2) the haematocrit was evaluated in six individual red knots after a flight of 1, 2, 4 and 10h in a wind tunnel and the data thus obtained compared with data on resting birds with or without food. In the four passerine species, the haematocrit decreased from 51% in fat birds to 48% in lean birds. In lean birds, the haematocrit dropped from 48% in birds with well-developed breast muscles to 36% in birds with emaciated breast muscles. In the red knots, the haematocrit was dependent on body mass in flying and resting birds. The haematocrit decreased from about 51% pre-flight to about 49% within 1h of flight and remained at this level for up to 10h of flight. Taking the results from the passerines and the red knots together, it seems that the haematocrit drops by a few percentage points within 1h after the onset of flight, decreases very slowly with decreasing body mass and decreases more steeply in very lean birds having entered stage III of fasting. This indicates that dehydration is not an underlying factor in decreased haematocrit because if this were the case we would expect an increase with endurance flight. We found no effect of the presence of blood parasites on haematocrit. With the onset of flight, haemodilution may be adaptive, because it reduces blood viscosity and, thereby, energy expenditure by the heart, or it may be a sign of water conservation as an insurance against the risk of dehydration during long non-stop flights. During endurance flight, a reduction in the haematocrit may be adaptive, in that oxygen delivery capacity is adjusted to the decreased oxygen needs as body mass decreases. A decreasing haematocrit would also allow birds to reduce heart beat frequency and/or heart size, because blood viscosity decreases disproportionally with decreasing haematocrit. However, when energy stores are about to come to an end and birds increase protein breakdown, the haematocrit decreases even further, and birds probably become anaemic due to a reduced erythropoiesis.
Convergent social structures can be found in taxa that split a long time ago, for example more than 230 Mio years ago as in
the case of mammals and birds. Such convergence is explained by common selection regimes, as all social systems are shaped
by sex-specific tactics and strategies to optimise their reproductive success. In addition, the major social mechanisms, brain
and physiology, are highly conserved throughout the vertebrates. Manoeuvring social contexts tends to be energetically costly
and, hence, favours efficient decision-making. Therefore, at least in vertebrates, complex social systems generally select
for social cognition. As an example for social convergence between mammals and birds, we introduce the surprisingly complex
social system of greylag geese, featuring components such as a female-bonded clan structure, long parent-offspring relationships,
as well as elaborate and highly functional patterns of mutual social support. Our results show that partners in reproductively
successful goose pairs are in hormonal synchrony and provide social support to each other. We suggest that social support
may be a major structuring principle of other social systems with long-term individualized and valuable partnerships as well.
In general, individual performance in social systems is determined by the interplay between proximate mechanisms and ultimate
functions.
The type or intensity of an immune response to a vaccine or a challenge can be influenced by intrinsic factors, such as age and sex of the individual, as well as extrinsic factors, such as environmental conditions, social interactions, type of diet, and exposure to toxicants. This chapter explores the non-genetic factors that influence the immune response of birds and focuses on the underlying mechanisms that mediate them. When possible, the impact of changes in immunity due to extrinsic factors on outcomes, such as susceptibility to infectious challenges or efficacy of vaccinations, is explored. Finally, methods for assessing the changes in immunity that result from non-genetic influences are discussed.
Passerine birds, especially during the breeding season and nestling development, are exposed to an array of hematophagous ectoparasites. Although the direct consequences of mite infestation on host fitness and immunological function have been investigated in the Domestic Chicken (Gallus gallus domesticus), parasite-specific immune responses to ectoparasites in passerine species have not been examined in great detail. We investigated the humoral immune response of House Sparrows (Passer domesticus) to hematophagous mite antigens and tested for the presence of mite-specific antibodies in adults, egg yolks, and nestlings in a wild population that was naturally exposed to ectoparasitic mites. Our results showed that adult House Sparrows can mount a specific adaptive immune response against hematophagous mite antigens. Further, we demonstrate that mite-specific antibodies are present in wild House Sparrow populations naturally infested with ectoparasites. The results of this study provide ecological immunologists with a tool for examining host-parasite interactions via a parasite-specific immune assay.
Breeding Wood Ducks (Aix sponsa) maintain pair-bonds later into the incubation period than most other species of North American ducks. We tested whether being paired was beneficial to females during incubation by comparing incubation constancy, incubation period, changes in female body mass, and reproductive success in a mate removal experiment. Females were assigned randomly to one of two treatments: paired controls (n = 24) or widowed (n = 21). Mates of females were removed early in incubation (̄ = day 5), and nests of paired and widowed females were equipped with temperature data loggers to record the presence and absence of incubating females. Paired and widowed females did not differ significantly with respect to incubation constancy, incubation period, body mass, or nesting and hatching success. Paired females, however, tended to produce second broods more often than widowed females. Being paired did not result in advantages to incubating females, but longer attendance by male Wood Ducks may benefit both sexes where breeding seasons are long and future reproductive opportunities (i.e., second broods) are more likely to occur.
There is intrinsic conflict between survival and reproduction. This conflict can be viewed from the perspective of the pace-of-life framework (an ultimate view), trading off many offspring per year over a short life against few offspring per year over a longer life; it can also be viewed from a resource-utilization perspective (a proximate view), increasing current reproductive effort vs. self-maintenance. The hypothalamicepituitaryeadrenal (HPA) axis controls the production of glucocorticoids (GCs) primarily responsible for mediating this proximate decision-making process. In field studies, GCs tend to decrease performance measures associated with reproduction, and increase measures associated with immediate survival. This chapter investigates the role of GCs in regulating reproductive effort (the proportion of available energy expended on reproductionda proximate query), approaching this question from an ultimate pace-of-life frame-work.
Diseased animals or those in poor condition are known to have reduced hematocrits. Many inves- tigators have assumed that hematocrit levels thus reflect condition and disease status of an animal. This study tested these assumptions by examining the relation between hematocrits of American kestrels (Falco sparuerius) during several stages of the breeding season, and condition, prey abundance, and blood parasite load. We also examined the potential effects of a number of intrinsic and extrinsic influences on hematocrit. Hematocrits did not differ between the sexes, or between the pre-laying and incubation periods. Among females, hematocrit did not vary with the date of sampling, breeding chronology, prey abundance, condition, age, or molt, although hematocrit increased with ambient temperature during incubation. Hematocrit of males was not related to breeding chronology, prey abundance, condition, age, or molt. During incubation, male hematocrit increased with the date of sampling and ambient temperature. Hematocrits of both sexes declined with the time of day that the sample was taken, and increased with the level of infection of the blood parasite Haemoproteus. The use of hematocrits to assess the health and condition of clinically normal kestrels is therefore questionable, and given the positive association with parasite loads, may even lead to erroneous conclusions. J. WILDL. MANAGE. 61(4):1297-1306
In mammals, support by a social partner may reduce stress levels and ease access to resources. We investigated the effects of the passive presence of a nearby social ally on excreted corticosterone immunoreactive metabolites and behaviour in juvenile graylag geese (Anser anser). Two groups of hand-raised juveniles (N1 = 9, N2 = 3) were tested over 1 year by positioning humans of different familiarity (i.e., the human foster parent, a familiar human, a nonfamiliar human, no human) at a standard distance to the focal geese. Their success in agonistic interactions significantly decreased with age and with decreasing familiarity of the accompanying human. The humans present modulated the excretion of corticosterone immunoreactive metabolites, with the strongest effects recorded after fledging when corticosterone metabolites were also positively correlated with agonistic behaviour. This suggests that a human foster parent may provide similar supportive benefits as goose parents do in natural families. We discuss the benefits of social alliances with regard to the integration into the flock, access to resources, and life history.
Waterfowl, whether free-living or in captivity, are hosts to a wide variety of internal and external parasites. With few exceptions, the significance of most parasitic infections is unknown, due, in part, to the fact that mixed parasitic infections are the rule rather than the exception. Therefore, effects of any one parasite species must be made in light of the other parasites, diseases, or stressors (eg, malnutrition) that may be present. Furthermore, the pathogenicity of a parasite may differ among species of birds as well as different populations of the same species. Experimental assessment of the effects of some parasites have been attempted using the mallard duck as the model; however, in light of species differences, the applicability of such studies to other species of waterfowl is unclear. Of the several hundred parasites that are present, nasal leeches, Leucocytozoon simondi, certain species of coccidia, some nematodes, the trematode Sphaeridiotrema globulus, cestodes in the genus Gastrotaenia, and some acanthocephalans have been associated with morbidity and/or mortality in captive or wild waterfowl. Detection of many parasitic infections can be accomplished through traditional diagnostic techniques (eg, fecal flotation, blood smears); however, the presence of parasites does not automatically equate with the presence of disease. Control and treatment measures are few, especially for free-ranging waterfowl. However, excellent sanitation can help combat many parasites in captive situations.
This review examines the avian heterophil leucocyte and provides a morphological and cytochemical profile drawn from light and electron microscopy studies of these cells and their characteristic cytoplasmic granules. Other aspects covered include relative and absolute heterophil counts in different avian species and the response of heterophils to stress and to acute inflammation. Heterophils are round cells and, with Romanowsky stains, their primary fusiform granules appear brick-red in colour. A secondary type of round granule, less dense in the electron microscope and smaller than the primary granule, can be seen in most avian species. The primary granules frequently display a ‘central body’ that may be proteinaceous in nature. Unlike mammalian neutrophils, avian heterophils are devoid of myeloperoxidase. However, their cytoplasmic granules contain several lysosomal and non-lysosomal enzymes including acid phosphatase, arylsulphatase, β-glucuronidase, phosphorylase, uridine diphosphate glucose-glucogen glycosyltrans-ferase, neutral and acid α-glucosidases, acid trimetaphosphatase and lysozyme. In the majority of birds heterophils are the second most numerous cell in circulation, the exceptions being several species of the Psittacine and Anseriformes orders, ostrich, ring-necked pheasant, pigeon and rosy flamingo. Heterophils generally outnumber lymphocytes in chicks between hatch and one week of age. Their numbers increase during mildly or moderately stressful conditions and consequently the heterophil/ymphocyte ratio can be used to detect the presence of physiological stress for most stressors. A heteropenia can occur, however, during severe stress. Heterophils respond to a stimulus (chemotactic agent) within about 30 minutes during the early inflammatory phase and they may also have sensitive and selective phagocytosing properties. By seven days heterophils become unrecognizable and, with macrophage recruitment, the characteristic heterophilic granuloma develops.
This review on avian blood leucocyte responses to stress covers the literature from the early 1980s. It considers only non-infectious hormonal responses of leucocytes to stress mediated either by nutritional, parenteral, climatic/environmental (physical or social) or psychological stressors. The heterophil/lymphocyte (H/L) ratio after the administration of ACTH either in the diet or by injection and during food restriction studies has been studied. The ratio was found to be inadequate during severe food restriction studies, as some stressed birds responded with a heteropenia, lymphocytosis and a significant basophilia. Climatic and environmental stressors such as road transportation and heat stress produced significantly raised H/L ratios and basophilias, respectively. Psychological stressors such as fasting, frustration or noise showed different leucocytic responses and the times in which cells were mobilized also varied. Although the H/L ratio is a less variable indicator of avian stress than individual cell numbers and more reliable than corticosteroid levels in plasma, this rule applies only when mild to moderate stress exists. During extreme stress, as in life-threatening situations, a heteropenia and basophilia develop so the H/L ratio cannot always be accepted as an accurate measurement of stress in poultry. Thus, in some avian stress a two-phase cellular reaction may be present. This biphasic leucocytic response to stress may be unique to Aves.
Male and female domestic chicks were housed in same-sex pairs until they were tested at 11 days of age. One chick was then removed from each established pair and the behavioral and adrenocortical responses of their remaining companions were measured. Social separation induced an overall increase in circulating corticosterone concentrations, thus illustrating its stressful properties. The isolation procedure appeared to have been equally distressing for males and females because no sex differences were found in plasma corticosterone levels either before or after separation. Female chicks vocalized sooner and ambulated more than males upon isolation but there were no detectable sex differences in ambulation latencies, peeping rates or jumping. The results are discussed in terms of social motivation, predator evasion, fear and attentional processes.
Families proved dominant over pairs, pairs over unpaired birds, and single males dominated single females. Single females with young ranked between families and pairs, and lone breeding males whose females were incubating ranked between pairs and unpaired individuals. The dominance value of pairs in winter correlated with subsequent fledging success, and there was some evidence that high-ranking males are more likely to obtain a mate. A positive feedback system 'age rt arrow dominance rt arrow fledging success rt arrow high dominance rt arrow fledging success' is suggested which could account for the 'delayed breeding' common in geese and swans. In pairs or families male age correlated more strongly than female age with winter dominance. Presence of the mate and/or offspring increases fighting motivation, thus explaining the dependence of rank on the social context. The hierarchy of social classes can be explained by geese signalling their degree of fighting motivation to each other. -from Author
In group living vertebrates, patterns of parasite infection vary within and between populations because of environmental and social factors. In the present study, we investigated patterns of parasite product excretion in graylag geese, focusing on environmental (season and temperature), individual (sex and age), and social factors (pair-bond status, reproductive state, and rearing condition). From March 2008 to May 2010, we collected 3574 samples from 171 individuals and analyzed them for nematode eggs and coccidian oocysts. Fecal samples that were infected with nematode eggs were also positive for coccidian oocyst to a higher rate. Fecal samples of goose-raised geese were positive for nematode eggs more often than those of hand-raised geese. In parental birds, the number of goslings fledged had a positive influence on the percentage of samples positive for nematode eggs. The number of samples infected with coccidian oocysts decreased with age. In parent birds, the number of samples found to be positive for coccidian oocysts decreased during the parental season, and female bird samples were positive more often than those of males. In graylag goslings, the number of fecal samples with coccidian oocysts was influenced by the goslings' age, with maximum excretion at 13 weeks. This is the first evidence to demonstrate an effect of a set of interacting environmental (e.g., season), individual (e.g., sex, age), and social (e.g., rearing condition, number of goslings fledged) factors on rate of parasite excretion in a socially complex bird. Our results suggest that socially stressful periods may have implications for individual health in graylag geese.
The effects of temporary male absence during egg laying on the production of extra-pair young by female eastern bluebirds,Sialia sialis, were examined. Females whose mates were removed for 2 days during egg laying produced more extra-pair young than did females whose mates were present during egg laying. Replacement males were observed at three of 11 nests from which resident males were temporarily removed, and one of 13 extra-pair young was sired by a replacement male. The increased production of extra-pair young when males were removed during egg laying suggests that (1) faced with apparent mate loss, females used copulations in an attempt to attract replacement males to care for young, (2) females were released from the constraints of mate guarding and sought extra-pair copulations, or (3) absence during egg laying reduced the ability of males to devalue rival sperm via supplemental copulations.
Les passereaux, en particulier durant la saison de reproduction et le développement des poussins, sont exposés à une gamme d'ectoparasites hématophages. Bien que les conséquences directes de l'acariose sur la condition physique et la fonction immunologique de l'hôte aient été étudiées chez Gallus gallus domesticus, les réponses immunitaires spécifiques aux ectoparasites chez les espèces de passereaux n'ont pas été examinées en détail. Nous avons étudié la réponse immunitaire humorale chez Passer domesticus face aux antigènes d'acariens hématophages et testé pour la présence d'anticorps spécifiques aux acariens chez les adultes, les vitellus et les poussins dans une population sauvage naturellement exposée aux acariens ectoparasites. Nos résultats montrent que les adultes peuvent présenter une réponse immunitaire adaptative spécifique contre les antigènes d'acariens hématophages. De plus, nous démontrons que les anticorps spécifiques aux acariens sont présents dans les populations sauvages de P. domesticus qui sont naturellement infestées par des ectoparasites. Les résultats de cette étude fournissent un outil aux immunologistes écologiques afin d'examiner les interactions hôte-parasite au moyen d'un test immunitaire spécifique au parasite.
Immune responses have evolved to defend hosts efficiently against the debilitating effects of parasites on host fitness. However, there are relatively few studies of the efficiency of the immune system in terms of providing hosts with an ability to defend themselves against parasitism. A meta-analysis of the literature on survival of birds in relation to non-specific immune response to challenge with an antigen or other measures of immune function demonstrated a mean effect adjusted for sample size of 0.43 across 12 studies. This observation shows that relatively simple estimates of non-specific immune responses often reliably predict a large and significant amount of variation in survivorship.
One group of commonly found parasites in birds, for which fitness consequences and effects on life history traits have been much debated are Haemosporidian blood parasites. In a long term study population of great reed warblers Acrocephalus arundinaceus in Sweden, previous studies have shown that the Haemosporidian blood parasites are in their chronic phase during the breeding season and that the fitness of infected and non-infected birds are similar. In the present study, we quantified parasite intensity (parasitemia) in 718 adults great reed warblers sampled between 1987 and 1998 for the three most common parasite species; Haemoproteus payevskyi (lineage GRW1), Plasmodium ashfordi (GRW2) and Plasmodium relictum (GRW4). We verified that the q-PCR method is accurately quantifying Haemoproteus payevskyi (GRW1) as it was highly correlated with the number of parasites seen under microscope. Frequency of mixed infections with two lineages was significantly higher than expected based on the prevalence of each of the three parasite lineages. The mean level of parasitemia was significantly different for the three lineages and individual birds had repeatable parasitemia levels between years. Females tended to have a higher parasitemia than males for all three parasite lineages combined. Females with higher GRW1 parasitemia tended to arrive later in spring to their breeding sites. There was a negative correlation between parasitemia and number of fledged offspring for GRW1, and a tendency for a negative correlation between GRW2 parasitemia and the proportion of recruiting offspring. Overall our results demonstrate that chronic Haemosporidian infections can have slight but significant effects on host life history traits, and therefore may act as important selective agents in wild bird populations.
Parasites and glucocorticoid hormones interact and affect a variety of processes within vertebrates, such as immune system function and reproduction. The nature of the relationship between parasite infection and glucocorticoid levels has received relatively little attention among free-ranging animals and results of experimental research in natural settings are equivocal. We conducted a parasite-reduction experiment to determine if reductions in nematodes or ectoparasites affect levels of faecal glucocorticoid metabolites (FGM) in adult raccoons. Individual raccoons were randomly assigned to a parasite-reduction treatment (ivermectin injection and Frontline Plus® application) or control group (saline injection) and recaptured within 30 days to assess treatment-related differences in parasitism and FGM levels. Treated animals had reduced nematode and ectoparasite communities. The most common and energetically expensive ectoparasite of raccoons in the region, the American dog tick, was reduced five-fold from an average of 19.3 ± 2.5 (se) to 3.4 ± 8 ticks per animal, and was unable to feed to repletion on treated animals. The prevalence of four out of seven nematode species was significantly lower in treated versus control animals; prevalence of these four nematodes ranged from 0 to 19% among treated animals and from 21 to 55% among control animals. The parasite infracommunity was also significantly reduced; the average number of nematode species per individual was 2.5 ± 0.3 in treated animals and 1.1 ± 0.2 in control animals, and the average number of ectoparasite species per individual was 2.3 ± 0.1 on treated animals and 1.1 ± 0.12 on control animals. No differences in FGM values were observed within individuals or between treatment and control groups following parasite-reduction treatments, indicating that the observed reductions in nematodes and ectoparasites had no effect on FGM levels of raccoons across the time frame of this study.
This chapter discusses the significance of the stress concept in gaining a better understanding of social mechanisms in nonhuman mammals. The development of this concept during the past years and the resulting present understanding of different stress reactions are described in the chapter. The triggers of stress reactions are mainly psychical processes resulting from the assessment of a situation by an individual. Dependent on the coping behavior of the individual, these processes lead to different physiological response patterns, which can result in a number of pathophysiological effects. The chapter introduces the most important currently applied methods in assessing stress levels in animals. Particular attention is paid to methodological problems, as well as to the limits of interpretation. The focal points of the chapter are the sympathetico–adrenomedullary and pituitary–adrenocortical systems, the pituitary–gonadal axis, and the immune system. An overview of the relationships between social situations and stress responses is provided, in which the research focuses on the monogamous and territorial tree shrews and the polygamous and territorial European wild rabbits. In these cases, the social rank of an individual, its sociopositive interactions with conspecifics, and the stability of the social system are determinants in the effects of a social situation on the individual's vitality and fertility.
Environmental stress has been suggested to increase host susceptibility to infections and reduce host ability to resist parasite growth and reproduction, thus benefiting parasites. This prediction stems from expected costs of immune defence; hosts in poor condition should have less resources to be allocated to immune function. However, the alternative hypothesis for response to environmental stress is that hosts in poor condition provide less resources for parasites and/or suffer higher mortality, leading to reduced parasite growth, reproduction and survival. We contrasted these alternative hypotheses in a trematode–snail (Diplostomum spathaceum–Lymnaea stagnalis) system by asking: (1) how host condition affects parasite reproduction (amount and quality of produced transmission stages) and (2) how host condition affects the survival of infected host individuals. We experimentally manipulated host condition by starving the snails, and found that parasites produced fewer and poorer quality transmission stages in stressed hosts. Furthermore, starvation increased snail mortality. These findings indicate that in well-established trematode infections, reduced ability of immune allocation has no effect on host exploitation by parasites. Instead, deteriorating resources for the snail host can directly limit the amount of resources available for the parasite. This, together with increased host mortality, may have negative effects on parasite populations in the wild.
A variety of factors are known to affect dominance and aggression in social vertebrates. In the present study, we used a long-term data set on greylag geese (Anser anser) to investigate the complex relationships between individual life histories, the social environment, and dominance-related behaviors. We applied a multifactorial approach to assess the relative importance of factors in different life-history stages. Previous studies in geese documented effects of sex and social status and achieved differing results for the effects of family size, age, and body weight on dominance and aggression. Extrinsic factors like season or flock structure were generally not considered. Our analyses showed that a considerable number of factors related to individual life histories, season, and the social environment affected dominance and aggression in greylag geese, but not all significant effects were necessarily strong effects. Pronounced effects on aggression rates were caused by the flock's sex ratio, parental effects, individual social status, and sex. Whether individuals interacted with the same opponents repeatedly was influenced most by parental effects and the sex ratio, whereas the strongest determinants of dominance rank were parental effects and social status. Hence, dominance behaviors may not only be influenced by intrinsic factors but also by season and an individual's social environment. Furthermore, our study indicates that optimal choices for achieving or maintaining a high dominance rank may vary considerably between life-history stages. This highlights the value of long-term studies and multifactorial approaches for understanding the complexities of dominance relationships in social vertebrates. Copyright 2011, Oxford University Press.
As in most social groups, agonistic interactions of various intensities are common in a goose flock. This may cause social stress, modulating heart rate (HR), which may serve as a measure of energetic investment and also of individual emotional involvement. We investigated HR responses to social encounters in 24 free-living greylag geese in an intact social environment. We recorded 1602 social interactions of various intensities in which the focal individual either attacked another member of the flock or was attacked itself. We analysed five HR parameters (mean HR, maximum HR, HR increase, duration until maximum, time until the baseline value was reached again). Generally, HR scaled positively with increasing intensity of agonistic interactions as well as with increasing duration. Individuals showed higher HRs when attacking than when being attacked. In addition, focal individuals responded with a greater HR increase when confronted with an opponent winning a higher percentage of interactions than itself. Repeated agonistic interactions against a specific opponent were related to greater HR responses than single events and focal individuals responded more strongly to male opponents than to females. Our results indicate a differential HR response depending on the intensity and duration of an interaction as well as the identity of the opponent. This differential physiological investment may reflect differences in emotional involvement depending on the social context of a particular agonistic interaction.
In this review, I focus on three key questions in avian comparative immunoecology: variation in immune responses in relation
to sex; latitude (and pace-of-life); and the annual cycle. I present hypotheses and evaluate the so far rather scanty and
heterogenic data to test them. Sex differences in immune responses have been hypothesized to be caused by inferior immune
responses in the heterogametic sex (females in birds), sexual selection (males invest more in mate acquisition and less in
immune function compared to females under polygyny, whereas the sexes invest equally in immune function under monogamy), or
body size differences. Available data refute the heterogametic sex hypothesis, but tentatively support the sexual selection
hypothesis. Latitudinal patterns of immune responses have been hypothesized to be adjusted to parasite pressure, pace-of-life
or breeding season stress. In passerine birds, species breeding closer to the equator (where parasites presumably are more
abundant) tended to show stronger humoral but not cell-mediated immune responses. Annual patterns of immune responses could
be related to melatonin levels or adjusted to seasonal differences in parasite exposure (high exposure in tropical migrants
in winter and in temperate breeding birds in summer). The results from studies of immune responses over the annual cycle in
birds show no clear pattern over the annual cycle and there is little consistency between different components of the immune
system. Clearly, to facilitate further testing of these intriguing ideas in comparative immunoecology, more studies on non-domesticated
birds are needed.
Most nonhuman primate species are remarkably social, but their social nature presents many challenges, including increased opportunities for pathogen transmission and development of disease (both physical and psychological). An interdisciplinary symposium was convened at the 2010 annual meeting of the American Society of Primatologists on the topic of social processes and disease in nonhuman primates, and four articles from that session, as well as a fifth that was separately solicited, appear in this special section. The articles reflect a variety of disciplines and perspectives that highlight the many ways that social processes can impact disease processes (and vice versa) in this highly social taxon. This is an increasingly active area of research interest as a consequence of technological developments and the availability of long-term field data. The continuing loss of primate habitat in the wild, climate change, and the need to manage high densities of primates in captivity, however, all add urgency to our need to better understand the bidirectional relationship between social factors and disease processes.