The Weddell seals of Larsen Harbour, South Georgia: a unique but apparently declining colony

Polar Record ◽  
2015 ◽  
Vol 51 (6) ◽  
pp. 667-671 ◽  
Author(s):  
Robert Burton
Keyword(s):  
Sea Ice ◽  
Breeding Season ◽  
Small Population ◽  
Single Observation ◽  
South Georgia ◽  
Weddell Seals ◽  
Cruise Ships

ABSTRACTThe small population of Weddell seals at Larsen Harbour, South Georgia, is isolated from the rest of the species and is unique because nearly all pups are born on land rather than on sea-ice. Observations of seals in Larsen Harbour during the breeding season are summarised. These have been infrequent until cruise ships started to visit. With often only a single observation in a year, accurate estimates of pup production are impossible but it appears that the population has decreased over the last three decades.

Proportional underwater call type usage by Weddell seals (Leptonychotes weddellii) in breeding and nonbreeding situations

2012 ◽  
Vol 90 (2) ◽  
pp. 237-247 ◽  
Author(s):  
Elyse E. Doiron ◽  
Philippe A. Rouget ◽  
John M. Terhune
Keyword(s):  
Sea Ice ◽  
Breeding Season ◽  
Ice Formation ◽  
Leptonychotes Weddellii ◽  
Mating Period ◽  
Call Type ◽  
Weddell Seals ◽  
Breeding Behaviour ◽  
Dark Conditions

Proportional underwater call type usage by Weddell seals ( Leptonychotes weddellii (Lesson, 1826)) near Mawson, Antarctica, investigated the hypothesis that certain call types function specifically in breeding behaviour. Recordings were collected at various sites in 2000 and 2002 from June to December. Twenty-four hour recordings were collected in 2002 at two sites. One hundred consecutive calls from each of 248 recordings were classified into one of ten common call types. Time to 100 calls provided the calling rate. The study period was divided into four periods representing initial sea-ice formation, pre-pupping, pupping, and mating. Calling rate and light–dark differences were also examined. No presence–absence differences were observed for any of the call types with season. The largest difference between nonbreeding and breeding situations was an increase from 32.2% to 38.1% for descending whistles (F[3,244] = 4.483, p = 0.004). Trills gradually increased from 1.8% to 7.3% toward the mating period (F[3,244] = 30.932, p < 0.001). The proportion of trills, chugs, descending whistles, and other call types also varied with calling rate and light–dark conditions. Some pre-reproductive behaviours may occur in winter, but no call types of Weddell seals function solely in the breeding season.

Sea-ice and density-dependent factors affecting foraging habitat and behaviour of Adélie penguins throughout the breeding season

2021 ◽  
Vol 168 (7) ◽  
Author(s):  
Nobuo Kokubun ◽  
Louise Emmerson ◽  
Julie McInnes ◽  
Barbara Wienecke ◽  
Colin Southwell
Keyword(s):  
Sea Ice ◽  
Breeding Season ◽  
Foraging Habitat ◽  
Factors Affecting ◽  
Density Dependent ◽  
Adélie Penguins

scholarly journals Dräktvariation hos hannar i skandinaviska populationer av svarthakad buskskvätta Saxicola rubicola

Ornis Svecica ◽  
2019 ◽  
Vol 29 ◽  
pp. 76-83
Author(s):  
Reino Andersson
Keyword(s):  
Breeding Season ◽  
Western Europe ◽  
Small Population ◽  
Genetic Differences ◽  
Lower Degree ◽  
British Isles ◽  
Individual Level ◽  
Norwegian Population ◽  
Large Distribution ◽  
Distribution In Europe

In western Europe, the European Stonechat Saxicola rubicola, occurs in two subspecies; rubicola, with a large distribution in Europe, and hibernans, mainly distributed on the British Isles. A small population of presumed hibernans birds breed in Norway. However, difficulties in distinguishing hibernans from rubicola at an individual level has led to speculation regarding the origin of the Norwegian birds. There are no clear genetic differences between the subspecies and their plumage appearance can be considered to overlap within parts of the range. To investigate this, I studied the plumage variation among males during the breeding season in the Scandinavian populations of European Stonechats in Sweden, Norway and Denmark. The study is based on photos of 404 males during the period March–May. The presence or absence of six typical hibernans characteristics were registered for each individual. The results show that males with both hibernans and rubicola characteristics occur during the spring in the Scandinavian populations. There was a clear over-representation of males with hibernans characteristics in Norway as compared to Sweden, and to a lower degree also to Denmark. If the expansion of rubicola progresses in Scandinavia, one could expect a larger proportion of rubicola-like males in the Norwegian population.

Territorial behavior and breeding frequency of male Weddell seals (Leptonychotes weddelli) in relation to age, size, and concentrations of serum testosterone and cortisol

1992 ◽  
Vol 70 (4) ◽  
pp. 680-692 ◽  
Author(s):  
Sherie S. Bartsh ◽  
Shirley D. Johnston ◽  
Donald B. Siniff
Keyword(s):  
Breeding Season ◽  
Coefficient Of Variation ◽  
Sexual Maturity ◽  
Serum Testosterone ◽  
Territorial Behavior ◽  
Competitive Behavior ◽  
Breeding Colony ◽  
Mcmurdo Sound ◽  
Weddell Seals ◽  
Transient Rise

The onset of sexual maturity and changes in weight and serum testosterone and cortisol concentrations were studied in male Weddell seals during October–December, 1986, at a breeding colony in McMurdo Sound, Antarctica. Ages were estimated from length or known from tagging history. Underwater copulatory and territorial activities were monitored by colored grease transfer and radiotelemetry, respectively. Hormone concentrations were measured by radioimmunoassay. Of 37 male seals visiting the colony, 22 were resident for ~5 weeks. About one-third of the male residents defended territories into estrus and were called territorial (T). Another one-third appeared unsuccessful at defending a territory and were called transitional (TN). The remaining one-third were nonterritorial (N). Males were closely matched in size (coefficient of variation ≤ 15% for length, girth, and weight). Most N males were 5–7 years old. T males (≥ 7 years old), being older (P < 0.05) than N males, attained 19 of 20 observed copulations. T males were heavier initially (P < 0.10) than TN or N males, and they lost more weight during the breeding season (P = 0.08, 3.2 vs. 2.1 kg/day) than N males. In all males, serum testosterone and cortisol concentrations declined, approaching nadir as estrus and the breeding season ended. Mean (±SE) daily concentrations ranged from 6.8 ± 2.4 ng/mL to nondetectable concentrations for testosterone and from 104.8 ± 13.2 to 54.7 ± 4.5 μg/dL for cortisol. Concentrations of both hormones were higher in T males than in N males. Hormone profiles of TN males initially resembled those of T males, but at estrus resembled those of N males. Coincident with a change in competitive behavior was a transient rise in cortisol accompanied by a drop in testosterone.

scholarly journals A review of the Santiago Purple Heron Ardea purpurea bournei, with a report of a new colony

1992 ◽  
Vol 2 (1) ◽  
pp. 15-23 ◽  
Author(s):  
C. J. Hazevoet
Keyword(s):  
Breeding Season ◽  
Total Population ◽  
Small Population ◽  
Climatic Conditions ◽  
Cape Verde ◽  
Educational Materials ◽  
Nest Sites ◽  
Large Trees ◽  
Nesting Site ◽  
Nesting Sites

SummaryThe Santiago Purple Heron Ardea (purpurea) bournei is endemic to the island of Santiago, Cape Verde Islands. In contrast to nominate purpurea, it nests high in the crowns of large trees. During the 1950s and 1960s, the total population was probably c. 75 pairs, mainly at the now defunct heronry at São Domingos. After the disappearance of that colony during the early 1970s, the only known nesting site was at Boa Entrada, Santa Catarina region, comprising less than 10 pairs. In January 1991, a new colony was discovered at Banana, Ribeira Montanha, with c. 20 recently used nests of which 2–3 had large young in January–February. The current population is thought not to exceed c. 20 pairs. Breeding occurs from late August to March. Apart from two old records in April, there are no records from the non-breeding season. Probably the birds disperse into the mountainous interior of the island after breeding and feed on the dry hillsides. The causes of the decline are unclear, but scarcity of suitable nest-sites and deteriorating climatic conditions may be significant. Because of the extremely small population, the birds and their nesting sites must be protected by law and the local people informed about the birds and their need for protection; educational materials are being developed.

scholarly journals Exploiting opportunistic observations to estimate changes in seasonal site use: an example with wetland birds

2016 ◽  
Author(s):  
Alejandro Ruete ◽  
Tomas Pärt ◽  
Åke Berg ◽  
Jonas Knape
Keyword(s):  
Breeding Season ◽  
Time Window ◽  
Main Tool ◽  
Probability Of Detection ◽  
High Rate ◽  
Sampling Effort ◽  
Single Observation ◽  
Occupancy Model ◽  
Site Use ◽  
Biodiversity Databases

Non-systematically collected, a.k.a. opportunistic, species observations are accumulating at a high rate in biodiversity databases. Occupancy models have arisen as the main tool to reduce effects of limited knowledge about effort in analyses of opportunistic data. These models are generally using long closure periods (e.g. breeding season) for the estimation of probability of detection and occurrence. Here we use the fact that multiple opportunistic observations in biodiversity databases may be available even within days (e.g. at popular birding localities) to reduce the closure period to one day in order to estimate daily occupancies within the breeding season. We use a hierarchical dynamic occupancy model for daily visits to analyse opportunistic observations of 71 species from nine wetlands during 10 years. Our model of daily colonization-extinction dynamics of species estimates within-season dynamics in occupancy at sites. We use the model to derive estimates of site use within seasons, in contrast to an annual occupancy estimates as produced in previous analyses of opportunistic data. Comparing results from our “seasonal site use model” to results from a traditional annual occupancy model (using a closure criterion of two months or more) showed that our model provide more detailed biologically relevant information. For example, when the aim is to analyse occurrences of breeding species, an annual occupancy model will over-estimate site use of species with temporary occurrences (e.g. migrants passing by, single itinerary prospecting individuals) as even a single observation during the closure period will be viewed as an occupancy. On the other hand, an occupancy model with within-season dynamics, such as our seasonal site use model will produce estimates of the extent to which sites are actually used. Model validation based on simulated data confirmed that our model is robust to certain changes and variability in sampling effort and species detectability. We conclude that for opportunistic data with many records (e.g. several reports per day almost every day), more information can be gained by reducing the time window of the closure criterion to acquire estimates of occupancies within seasons.

scholarly journals Exploiting opportunistic observations to estimate changes in seasonal site use: an example with wetland birds

2016 ◽  
Author(s):  
Alejandro Ruete ◽  
Tomas Pärt ◽  
Åke Berg ◽  
Jonas Knape
Keyword(s):  
Breeding Season ◽  
Time Window ◽  
Main Tool ◽  
Probability Of Detection ◽  
High Rate ◽  
Sampling Effort ◽  
Single Observation ◽  
Occupancy Model ◽  
Site Use ◽  
Biodiversity Databases

Non-systematically collected, a.k.a. opportunistic, species observations are accumulating at a high rate in biodiversity databases. Occupancy models have arisen as the main tool to reduce effects of limited knowledge about effort in analyses of opportunistic data. These models are generally using long closure periods (e.g. breeding season) for the estimation of probability of detection and occurrence. Here we use the fact that multiple opportunistic observations in biodiversity databases may be available even within days (e.g. at popular birding localities) to reduce the closure period to one day in order to estimate daily occupancies within the breeding season. We use a hierarchical dynamic occupancy model for daily visits to analyse opportunistic observations of 71 species from nine wetlands during 10 years. Our model of daily colonization-extinction dynamics of species estimates within-season dynamics in occupancy at sites. We use the model to derive estimates of site use within seasons, in contrast to an annual occupancy estimates as produced in previous analyses of opportunistic data. Comparing results from our “seasonal site use model” to results from a traditional annual occupancy model (using a closure criterion of two months or more) showed that our model provide more detailed biologically relevant information. For example, when the aim is to analyse occurrences of breeding species, an annual occupancy model will over-estimate site use of species with temporary occurrences (e.g. migrants passing by, single itinerary prospecting individuals) as even a single observation during the closure period will be viewed as an occupancy. On the other hand, an occupancy model with within-season dynamics, such as our seasonal site use model will produce estimates of the extent to which sites are actually used. Model validation based on simulated data confirmed that our model is robust to certain changes and variability in sampling effort and species detectability. We conclude that for opportunistic data with many records (e.g. several reports per day almost every day), more information can be gained by reducing the time window of the closure criterion to acquire estimates of occupancies within seasons.

On the mating system of polar bears

1986 ◽  
Vol 64 (10) ◽  
pp. 2142-2151 ◽  
Author(s):  
Malcolm A. Ramsay ◽  
Ian Stirling
Keyword(s):  
Sex Ratio ◽  
Sea Ice ◽  
Mating System ◽  
Breeding Season ◽  
Large Body ◽  
Arctic Sea Ice ◽  
Polar Bears ◽  
Adult Males ◽  
Terrestrial Mammals ◽  
Adult Females

Polar bears are intimately associated with arctic sea ice and their distribution is approximated by its winter extent. They are the only terrestrial mammals, other than humans, to have adapted so completely to sea ice, a quite different habitat, spatially and temporally, from that occupied by other terrestrial mammals. We propose that the dynamics of sea ice and the associated variability in access to food have played a major role in the evolution of the social structure and mating system of polar bears. Adult females and males move to areas of the sea ice where the greatest success in hunting is realized. Such regions are unpredictable in location, however, both seasonally and annually. Because female distributions are unpredictable, adult males are unable to defend stable territories that will encompass the home ranges of one or more females and may instead distribute themselves among different sea-ice habitats at the same relative densities as solitary adult females. Females keep nursing cubs with them for more than 1 year; hence the mean interbirth interval is 2 or more years. This results in a functionally skewed sex ratio, with fewer females available to breed in any one year than males, and in intrasexual competition among males for access to breeding females. Consequently, established dominance hierarchies among males are unstable, and wounding, scarring, and breakage of canine teeth are common; these are evidence of direct physical confrontations during the breeding season. Large body size is advantageous in these fights and this has resulted in one of the highest degrees of sexual dimorphism among terrestrial mammals. Because of the funtionally skewed sex ratio and the shifting distribution of both females and males, however, even the largest male probably cannot be certain of locating a larger than average number of receptive females in any one breeding season.

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