Natal Area Research Articles

Linking Canadian Harvested Juvenile American Black Ducks to Their Natal Areas Using Stable Isotope (δD, δ13C, and δ15N) Methods

Ashley, P., K. A. Hobson, S. L. VanWilgenburg, N. North, and S. Allan Petrie. 2010. Linking Canadian harvested juvenile American black ducks to their natal areas using stable isotope (δd, δ13c, and δ15n) methods. Avian Conservation and Ecology 5(2): 7.http://dx.doi.org/10.5751/ACE-00397-050207

Social influences on dispersal and the fat-tailed dispersal distribution in red-cockaded woodpeckers

‘‘Fat-tailed’’ distributions of dispersal distances involve long movements that do not appear to follow the normal distributioncharacterizing most short dispersals. Theorists have offered 2 nonexclusive explanations for such distributions. They suggest thatthe fat tail is a product of a single perturbed dispersal function, or that there may be multiple movement modes that widen dis-persal distributions, or kernels, when considered simultaneously. We evaluated dispersal distances in the cooperatively breedingred-cockaded woodpecker (Picoides borealis) using a 22-year data set. Results illustrated that dispersal distances differed betweenjuvenile and helper dispersers but not between sexes. Results further showed fat-tailed dispersal distributions in all social and sexclasses. Then within juvenile females, we used radiotelemetry to document 2 fundamentally different dispersal strategies: Wood-peckers forayed from a natal area until breeding vacancies were located, and they made jumps to distant locations where birdscontinued to search for settlement options. Jumping was a behavior that added long-distance movements to the dispersal kerneland fattened the tail of the distribution. Our results are congruent with growing evidence that dispersal of animals typically doesnot represent a single process and that dispersers may switch between movement modes based on a complex relationship ofinternal state, landscape characteristics, motion capacity, and navigational ability. Rare and cryptic movement modes such asjumping may also account for the fat tail in the dispersal distance distributions of other species. Key words: dispersal, fat taildistribution, kurtosis, movement ecology, Picoides borealis, red-cockaded woodpecker. [Behav Ecol]

Summer distribution and abundance of juvenile Chinese horseshoe crabs Tachypleus tridentatus along an intertidal zone in southern China

Owing to human exploitation, pollution and loss of breeding and nursery grounds, Chinese horseshoe crabs Tachypleus tridentatus are facing the risk of population decline and even- tual extinction. In order to provide baseline information needed to formulate future conservation strategies, we examined the spatial distribution, densities and carapace width of juvenile T. tridenta- tus along 6 transects at an intertidal zone of Beibu Gulf, South China Sea, during the summer of 2008. The environmental parameters measured (water temperature, salinity and dissolved oxygen) did not vary significantly among transects. However, the abundance and size distribution of juvenile T. tri- dentatus was statistically different between transects. Juvenile T. tridentatus prefer to move further from their natal area as they grow: therefore, smaller juveniles tend to be distributed closer to the shore, while larger juveniles are located further offshore.

Effects of temperature on disease progression and swimming stamina in Ichthyophonus‐infected rainbow trout, Oncorhynchus mykiss (Walbaum)

Rainbow trout, Oncorhynchus mykiss, were infected with Ichthyophonus sp. and held at 10 degrees C, 15 degrees C and 20 degrees C for 28 days to monitor mortality and disease progression. Infected fish demonstrated more rapid onset of disease, higher parasite load, more severe host tissue reaction and reduced mean-day-to-death at higher temperature. In a second experiment, Ichthyophonus-infected fish were reared at 15 degrees C for 16 weeks then subjected to forced swimming at 10 degrees C, 15 degrees C and 20 degrees C. Stamina improved significantly with increased temperature in uninfected fish; however, this was not observed for infected fish. The difference in performance between infected and uninfected fish became significant at 15 degrees C (P = 0.02) and highly significant at 20 degrees C (P = 0.005). These results have implications for changes in the ecology of fish diseases in the face of global warming and demonstrate the effects of higher temperature on the progression and severity of ichthyophoniasis as well as on swimming stamina, a critical fitness trait of salmonids. This study helps explain field observations showing the recent emergence of clinical ichthyophoniasis in Yukon River Chinook salmon later in their spawning migration when water temperatures were high, as well as the apparent failure of a substantial percentage of infected fish to successfully reach their natal spawning areas.

Downstream Migrations of Juvenile Salmon and Other Fishes in the Upper Yukon River

The Yukon River is the fourth largest river in North America, yet the ecology of its fishes has not been well described. During the spring and summer of 2002– 04, we sampled the downstream migrations of fishes in the Yukon River mainstem near the Canada-U.S. border, using a rotary auger trap. Age-0 juvenile chinook salmon, Oncorhynchus tshawytscha, were the most common fish in the catch, and they peaked in abundance in mid-June. Smaller numbers of age-1 chinook salmon and age-0 chum salmon, O. keta, were caught earlier in the season. Over 80% of the remaining catch consisted of young-of-theyear Coregoninae (whitefish), presumably moving from natal areas to summer rearing habitats. Few adult whitefish were captured, probably because our sampling terminated before fall spawning migrations began. Both juveniles and adults were captured for six other winter or spring spawning species that we encountered. Our results indicate that the Yukon River mainstem is used extensively as a migration corridor. This reach of the mainstem has very high suspended sediment levels in summer; its significance as rearing habitat remains unknown. Further studies are required to delineate the extent of migrations and the population structure for the non-anadromous species.

Long‐term natal site‐fidelity by immature lemon sharks (Negaprion brevirostris) at a subtropical island

Although many sharks begin their life confined in nursery habitats, it is unknown how rapidly they disperse away from their natal area once they leave the nursery. We examine this issue in immature lemon sharks (Negaprion brevirostris) from the time they leave the nursery (approximately age 3) at a subtropical island (Bimini, Bahamas), through to the onset of sexual maturity (approximately age 12). From 1995 to 2007 we tagged and genotyped a large fraction of the nursery-bound sharks at this location (0-3 years of age, N = 1776 individuals). From 2003 to 2007 we sampled immature sharks aged from 3 to 11 years (N = 150) living around the island and used physical/genetic tag recaptures coupled with kinship analysis to determine whether or not each of these 'large immature sharks' was locally born. We show that many island-born lemon sharks remain close to their natal area for long periods (years) after leaving the nursery; more than half of the sampled sharks up to 135 cm total length ( approximately 6 years old) were locally born. The fraction of locally born sharks gradually declined with increasing shark size, indicating that dispersal is relatively slow and does not primarily occur after sharks reach a threshold size. Local conservation measures (e.g. localized fishery closures, marine protected areas) can therefore help protect island-born lemon sharks even after they leave the nursery habitat.

Effect of hair removal by Nd:YAG laser on the recurrence of pilonidal sinus

Pilonidal sinus (PNS) is chronic inflammatory process of the skin in the natal cleft. Management of PNS is mainly surgical. Although different types of surgery have been performed, the recurrence rate is still high. To evaluate the effectiveness of laser hair removal (LHR) in the natal cleft area on the recurrence rate of PNS as an adjuvant therapy after surgical treatment. Twenty five patients with PNS were included in this study. Fifteen patients underwent LHR treatment using Nd:YAG laser after surgical excision of PNS (Patients group) while ten subjects with PNS did not do LHR and served as a control group. All of the patients were male patients. Their age ranged from 17 to 29 years with a mean of 21.60 +/- 3.13 years. They had Fitzpatrick skin type III, IV and V. The patients have got 3 to 8 sessions of LHR (mean 4.87 +/- 1.64). Follow up period lasted between 12 to 23 months. None of the patients, who underwent LHR, has required further surgical treatment to date. Seven patients out of ten in the control group have developed recurrent PNS. Pain was the most frequent side effect and it was seen in 6 patients (40%). LHR can prevent the recurrence of PNS. LHR should be advised as an essential adjuvant treatment after surgical excision of PNS. In non-complicated recurrent PNS, LHR is strongly advocated to be started before and continued after doing surgical treatment.

Natal dispersal of hazel grouse Bonasa bonasia in relation to habitat in a temperate forest of South Korea

Natal dispersal and habitat selection of hazel grouse Bonasa bonasia juveniles were assessed by radio tracking in a temperate forest of South Korea during June 2003–November 2006. The birds used in the dispersal analysis ( n = 43), 88% of birds dispersed. The average dispersal of hazel grouse from the natal area was 2231 ± 494 m (mean ± SD); range 134–6267 m. There were no significant differences in dispersal rate and distance between sexes. Hazel grouse’ habitat use differed from random use of available natal dispersals. In this natal dispersal scale of habitat selection, natural deciduous forest ranked highest, followed by mixed forest, coniferous plantation, deciduous plantation and others (rock and bare lands). We found that in general, the hazel grouse is an active disperser. Knowledge of aspects of habitat use that are relevant to dispersal may provide a better assessment of the fitness effects of dispersal in proximate and ultimate terms.

Mechanisms of Population Heterogeneity Among Molting Common Mergansers on Kodiak Island, Alaska: Implications for Genetic Assessments of Migratory Connectivity

Abstract. Quantifying population genetic heterogeneity within nonbreeding aggregations can inform our understanding of patterns of site fidelity, migratory connectivity, and gene flow between breeding and nonbreeding areas. However, characterizing mechanisms that contribute to heterogeneity, such as migration and dispersal, is required before site fidelity and migratory connectivity can be assessed accurately. We studied nonbreeding groups of Common Mergansers (Mergus merganser) molting on Kodiak Island, Alaska, from 2005 to 2007, using banding data to assess rates of recapture, mitochondrial (mt) DNA to determine natal area, and nuclear microsatellite genotypes to assess dispersal. Using baseline information from differentiated mtDNA haplogroups across North America, we were able to assign individuals to natal regions and document population genetic heterogeneity within and among molting groups. Band-recovery and DNA data suggest that both migration from and dispersal among natal areas contribute to admi...

Natal Dispersal By Pygmy Rabbits (Brachylagus idahoensis)

Multiple factors likely influence natal dispersal behavior of juvenile mammals, which is typically male-biased. Because of their small body size and specific habitat requirements, pygmy rabbits (Brachylagus idahoensis) are expected to exhibit limited dispersal. We predicted that dispersal would be male-biased, that juveniles born later in the year would disperse farther, and that juveniles would be more likely to disperse away from areas of higher habitat saturation. We used radiotelemetry to study dispersal of 61 juvenile pygmy rabbits (31 males and 30 females) from shortly after emergence from natal burrows (April‐July) to the beginning of the next breeding season (mid-March) during 2004‐2006. Juveniles dispersed before 12 weeks of age, and typically completed dispersal movements within 1 week. Both sexes exhibited a high rate of dispersal (males ¼ 90%; females ¼ 80%); however, juvenile females settled more than 3 times farther from their natal areas than males. Median natal dispersal distances for males and females were 1.0 km (range ¼ 0.03‐6.5 km) and 2.9 km (range ¼ 0.02‐11.9 km), respectively. Dispersing juveniles crossed gravel roads and perennial streams; however, rabbits tended to initiate dispersal movements away from nearby streams. Mortality rates for male and female juvenile rabbits were 69.2% and 88.5%, respectively, and were highest during the first 2 months after emergence from the natal burrow. We found no evidence that date of emergence, body condition, or habitat saturation influenced dispersal frequency or distance in juvenile pygmy rabbits. Results indicate that pygmy rabbits are capable of dispersing long distances and suggest that their conservation will require land management at broader spatial extents.

Movements of juvenile Bonelli's Eagles Aquila fasciata during dispersal

Capsule Juvenile non‐breeding males and females explored surrounding areas, returned to breeding areas, and settled in temporary settlement areas. Aims To describe movement patterns of juvenile Bonelli's Eagles during the transient phase of dispersal. Methods Radiotelemetry data from 16 individuals were studied. Results Six main temporary settlement areas were located. No sex differences were found in the time to first departure from natal areas, time to the first temporary settlement, or time of the first return to natal areas. Juvenile eagles did not settle in temporary settlement areas until they were, on average, 245 days old. In general, males and females did not differ in their movement patterns during the early part of the dispersal period. However, after approximately 500 days males spent 60.8% of their time exploring surrounding areas, probably with the aim of searching for vacant territories or mates, whereas females of the same age devoted 26.7% of their time to exploration. Conclusion Movements and use of sites during the transient phase of dispersal are complex. They have important implications for the conservation of this endangered species.

Informed dispersal, heterogeneity in animal dispersal syndromes and the dynamics of spatially structured populations

There is accumulating evidence that individuals leave their natal area and select a breeding habitat non-randomly by relying upon information about their natal and future breeding environments. This variation in dispersal is not only based on external information (condition dependence) but also depends upon the internal state of individuals (phenotype dependence). As a consequence, not all dispersers are of the same quality or search for the same habitats. In addition, the individual's state is characterized by morphological, physiological or behavioural attributes that might themselves serve as a cue altering the habitat choice of conspecifics. These combined effects of internal and external information have the potential to generate complex movement patterns and could influence population dynamics and colonization processes. Here, we highlight three particular processes that link condition-dependent dispersal, phenotype-dependent dispersal and habitat choice strategies: (1) the relationship between the cause of departure and the dispersers' phenotype; (2) the relationship between the cause of departure and the settlement behaviour and (3) the concept of informed dispersal, where individuals gather and transfer information before and during their movements through the landscape. We review the empirical evidence for these processes with a special emphasis on vertebrate and arthropod model systems, and present case studies that have quantified the impacts of these processes on spatially structured population dynamics. We also discuss recent literature providing strong evidence that individual variation in dispersal has an important impact on both reinforcement and colonization success and therefore must be taken into account when predicting ecological responses to global warming and habitat fragmentation.

Families in space: relatedness in the Barents Sea population of polar bears (Ursus maritimus)

The kin structure and dispersal pattern of polar bears (Ursus maritimus) of the Barents Sea was investigated during the spring mating season using two complementary approaches. First, individual genotypes based on the analyses of 27 microsatellite loci of 583 polar bears were related to field information gathered from 1146 bears in order to reconstruct the animals' pedigrees and to infer geographical distances between adult bears of different relatedness categories. According to the data, the median natal dispersal distance of the male animals was 52 km while that of the females was 93 km. Second, the relatedness of pairs of adult bears was estimated and correlated to the geographical distance between them. The female dyads had a much stronger kin structure than the male dyads. The 'pedigree approach' revealed a male kin structure which could not be detected using the 'relatedness approach'. This suggests that, on a broader scale, effective dispersal is slightly male biased. Despite fidelity to natal areas, male-mediated gene flow may nevertheless prevent genetic differentiation. Males might occasionally shift their home range which could therefore lead to a male-biased breeding dispersal. Our results showed that a nonterritorial species such as the polar bear that has a high dispersal potential, lives in a highly unstable environment and migrates seasonally is still able to exhibit a distinct kin structure during the mating season.

Movements of Juvenile Gyrfalcons from Western and Interior Alaska Following Departure from Their Natal Areas

Juvenile raptors often travel thousands of kilometers from the time they leave their natal areas to the time they enter a breeding population. Documenting movements and identifying areas used by raptors before they enter a breeding population is important for understanding the factors that influence their survival. In North America, juvenile Gyrfalcons (Falco rusticolus) are routinely observed outside the species' breeding range during the nonbreeding season, but the natal origins of these birds are rarely known. We used satellite telemetry to track the movements of juvenile Gyrfalcons during their first months of independence. We instrumented nestlings with lightweight satellite transmitters within 10 d of estimated fledging dates on the Seward Peninsula in western Alaska and in Denali National Park (Denali) in interior Alaska. Gyrfalcons spent an average of 41.4 ± 6.1 d (range = 30–50 d) in their natal areas after fledging. The mean departure date from natal areas was 27 August ± 6.4 d. We tracked 15 individuals for an average of 70.5 ± 28.1 d post-departure; Gyrfalcons moved from 105 to 4299 km during this period and tended to move greater distances earlier in the tracking period than later in the tracking period. Gyrfalcons did not establish temporary winter ranges within the tracking period. We identified several movement patterns among Gyrfalcons, including unidirectional long-distance movements, multidirectional long- and short-distance movements, and shorter movements within a local region. Gyrfalcons from the Seward Peninsula remained in western Alaska or flew to eastern Russia with no movements into interior Alaska. In contrast, Gyrfalcons from Denali remained in interior Alaska, flew to northern and western Alaska, or flew to northern Alberta. Gyrfalcons from both study areas tended to move to coastal, riparian, and wetland areas during autumn and early winter. Because juvenile Gyrfalcons dispersed over a large geographic area and across three international boundaries, conservation efforts should focus on both regional and international scales.

Post-Fledging Movements of Juvenile Common Mergansers(Mergus merganser)in Alaska as Inferred by Satellite Telemetry

Abstract We implanted satellite transmitters into eight juvenile Common Mergansers to investigate post-fledging movements from their natal river in southcentral Alaska. Subsequently, they moved widely throughout portions of western and southcentral Alaska up to 750 km from their natal areas during fall and winter months. Transmitters of two birds (one male and one female) continued to send location data into their second year and allowed us to determine the location and timing of the flightless molt period for each bird. Overall, our data suggest that juvenile Common Mergansers range widely immediately after fledging, that second year males and females may differ in their movement patterns, and that these movements have implications for population genetic structure of this species.

Geomagnetic imprinting: A unifying hypothesis of long-distance natal homing in salmon and sea turtles

Several marine animals, including salmon and sea turtles, disperse across vast expanses of ocean before returning as adults to their natal areas to reproduce. How animals accomplish such feats of natal homing has remained an enduring mystery. Salmon are known to use chemical cues to identify their home rivers at the end of spawning migrations. Such cues, however, do not extend far enough into the ocean to guide migratory movements that begin in open-sea locations hundreds or thousands of kilometers away. Similarly, how sea turtles reach their nesting areas from distant sites is unknown. However, both salmon and sea turtles detect the magnetic field of the Earth and use it as a directional cue. In addition, sea turtles derive positional information from two magnetic elements (inclination angle and intensity) that vary predictably across the globe and endow different geographic areas with unique magnetic signatures. Here we propose that salmon and sea turtles imprint on the magnetic field of their natal areas and later use this information to direct natal homing. This novel hypothesis provides the first plausible explanation for how marine animals can navigate to natal areas from distant oceanic locations. The hypothesis appears to be compatible with present and recent rates of field change (secular variation); one implication, however, is that unusually rapid changes in the Earth's field, as occasionally occur during geomagnetic polarity reversals, may affect ecological processes by disrupting natal homing, resulting in widespread colonization events and changes in population structure.

Magnetic features of marine black turtle natal beaches and im- plications for nest selection


 
 
 The beaches of Colola and Maruata, Michoaca?n, southern Me?xico are nesting places of the marine black turtle, Che- lonia agassizi. Marine turtles use magnetic cues to orient their long distance navigation, and might also use magnetic such to refine their geographical position within their natal area. We present results on the characterization of nesting beaches in terms of magnetic properties. Hysteresis parameters may allow distinguishing nesting from non-nesting beaches. The results may have implications for the selection and identification of nesting sites by marine black turtles, in the context of magnetic orientation mechanisms.
 
 

Placing butterflies on the map – testing regional geographical resolution of three stable isotopes in Sweden using the monophagus peacock Inachis io

Stable isotope analyses of tissues have been used to help delineate natal regions and routes of migratory animals. The foundations of such studies are isotopic gradients or differences representing geographic regions and habitat used by the organism that are retained in selected tissues. We sampled peacock butterflies Inachis io on a regional level in southern Sweden to study natural variation and the resolving power of the stable isotope method to delineate individuals from known areas on a smaller scale than has typically been used in previous studies. Hydrogen (δD), carbon (δ13C) and nitrogen (δ15N) isotopes were obtained from butterflies at seven different locations in an area of 250×250 km over three years (2002–2004). We found sufficient isotopic differences on this regional scale to delineate approximate origins. Of the three isotopes, deuterium showed good discrimination between sites, carbon isotopes showed weaker differentiation, whereas nitrogen isotopes proved unsuitable for small scale studies in this region due to high and unpredictable variation. We found there was enough variation in δD between years to prevent a general application of the technique to resolve sub‐regional variation. Substantial part of this variation was probably caused by seasonal changes in δD of precipitation. These differences produce significant variation in δD between years in animals having short and variable tissue development times, and are difficult to estimate in natural situations. We conclude that stable isotopes are potentially powerful predictors for studies of migratory butterflies in Europe. However, without good knowledge about the sampled individuals’ previous life‐history, a lot of the natural environmental variation in tissue δD cannot be controlled for. In the case of migratory species, this information is difficult to obtain, making the confidence intervals for prediction of natal areas fairly wide and probably only suitable for longer distance migration.

Fidelity and breeding probability related to population density and individual quality in black brent geese Branta bernicla nigricans

1. Patterns of temporary emigration (associated with non-breeding) are important components of variation in individual quality. Permanent emigration from the natal area has important implications for both individual fitness and local population dynamics. 2. We estimated both permanent and temporary emigration of black brent geese (Branta bernicla nigricans Lawrence) from the Tutakoke River colony, using observations of marked brent geese on breeding and wintering areas, and recoveries of ringed individuals by hunters. We used the likelihood developed by Lindberg, Kendall, Hines & Anderson 2001 (Combining band recovery data and Pollock's robust design to model temporary and permanent emigration. Biometrics, 57, 273-281) to assess hypotheses and estimate parameters. 3. Temporary emigration (the converse of breeding) varied among age classes up to age 5, and differed between individuals that bred in the previous years vs. those that did not. Consistent with the hypothesis of variation in individual quality, individuals with a higher probability of breeding in one year also had a higher probability of breeding the next year. 4. Natal fidelity of females ranged from 0.70 +/- 0.07-0.96 +/- 0.18 and averaged 0.83. In contrast to Lindberg et al. (1998), we did not detect a relationship between fidelity and local population density. Natal fidelity was negatively correlated with first-year survival, suggesting that competition among individuals of the same age for breeding territories influenced dispersal. Once females nested at the Tutakoke River, colony breeding fidelity was 1.0. 5. Our analyses show substantial variation in individual quality associated with fitness, which other analyses suggest is strongly influenced by early environment. Our analyses also suggest substantial interchange among breeding colonies of brent geese, as first shown by Lindberg et al. (1998).

Temporal and Spatial Variability in Otolith Trace‐Element Signatures of Juvenile Striped Bass from Spawning Locations in Lake Texoma, Oklahoma‐Texas

AbstractWe assessed the potential of trace‐element analysis for identifying spawning locations of striped bass Morone saxatilis in the two tributaries of Lake Texoma, Oklahoma‐Texas, during 2002‐2004. We also assessed the temporal stability of elemental signatures over 3 years. Elemental composition of juvenile striped bass otoliths varied considerably between the two tributary arms of Lake Texoma both within and among years. Overall reclassification rates within each collection year ranged between 81% and 93%. However, because of high interannual variability, classification functions could not reliably predict natal areas for individuals from other year‐classes (19‐62%). Although the mechanisms generating spatial and temporal differences in otolith chemistry are not well understood, spatial differences in otolith chemistry indicate that elemental fingerprints of striped bass from the two natal rivers in the Lake Texoma system provide natural tags of juvenile habitat. The temporal variability we observed in otolith elemental signatures complicates the use of these signatures for determining the natal river of an unknown individual from an unsampled year‐class. However, building a library of trace‐element signatures for yearly cohorts should make it possible to determine natal rivers for adult striped bass from known cohorts.