Rainfall in prior breeding seasons influences population size of a small marsupial

2012 ◽  
Vol 38 (5) ◽  
pp. 581-591 ◽  
Author(s):  
HANIA LADA ◽  
JAMES R. THOMSON ◽  
SHAUN C. CUNNINGHAM ◽  
RALPH MAC NALLY
Keyword(s):  
Population Size ◽  
Breeding Seasons

scholarly journals Range contraction in the pampas meadowlark Sturnella defilippii in the southern pampas grasslands of Argentina

Oryx ◽  
2004 ◽  
Vol 38 (2) ◽  
pp. 164-170 ◽  
Author(s):  
Fabián M. Gabelli ◽  
Gustavo J. Fernández ◽  
Valentina Ferretti ◽  
Gabriela Posse ◽  
Eugenio Coconier ◽  
...  
Keyword(s):  
Population Size ◽  
Grassland Bird ◽  
Range Contraction ◽  
Habitat Transformation ◽  
Preferred Habitat ◽  
Extensive Field ◽  
Population Reduction ◽  
Natural Grasslands ◽  
Nesting Site ◽  
Breeding Seasons

The Vulnerable Pampas meadowlark Sturnella defilippii (Family Icteridae) is a Neotropical grassland bird that suffered a severe population reduction and range contraction during the 20th century. Formerly distributed across most of the pampas grasslands, it is now confined to the southern tip of its original range. There are small groups of wintering birds in southern Brazil, a small reproductive population in eastern Uruguay, and the main reproductive population occurs on the southern pampas grasslands of Argentina. In this paper we report the results of an extensive field survey of these southern pampas grasslands, carried out to estimate the pampas meadowlark's population size and to identify the factors potentially responsible for its range contraction. During the 1999 breeding season we surveyed a total of 296 sample locations (transects, randomly selected points, and sites checked for nesting site reoccupation). We found 66 reproductive groups of pampas meadowlarks. The minimum population size and extent of occurrence were estimated to be 28,000 individuals and 4,810 km2, respectively. This value represents a range contraction of c. 30% compared to that estimated in a study carried out between 1992 and 1996. Pampas meadowlarks reoccupied natural grassland sites for nesting that were used in previous breeding seasons when these sites remained undisturbed. Habitat transformation appears to be the main factor causing the range contraction of the pampas meadowlark. We suggest that long-term monitoring of this population and its preferred habitat, the natural grasslands, is required in order to ensure the conservation of this species.

scholarly journals Hooded Grebe Podiceps gallardoi population decreased by eighty per cent in the last twenty-five years

2012 ◽  
Vol 22 (4) ◽  
pp. 371-382 ◽  
Author(s):  
IGNACIO ROESLER ◽  
SANTIAGO IMBERTI ◽  
HERNÁN CASAÑAS ◽  
BETTINA MAHLER ◽  
JUAN CARLOS REBOREDA
Keyword(s):  
Population Size ◽  
Breeding Season ◽  
Low Temperatures ◽  
Buenos Aires ◽  
American Mink ◽  
Santa Cruz ◽  
Southern Patagonia ◽  
Conservation Actions ◽  
Strong Winds ◽  
Breeding Seasons

SummaryWe estimated the present population size of the Hooded Grebe Podiceps gallardoi and compared it with the population in 1985. During the breeding seasons 2009/2010 and 2010/2011 we monitored 251 lakes on the main plateaus of Santa Cruz province, southern Patagonia, Argentina, where the entire population of Hooded Grebes spends the breeding season. During 2009/2010 we monitored 131 lakes and observed 521 Hooded Grebes in 16 lakes, while during 2010/2011 we monitored 186 lakes and observed 535 individuals in 14 lakes. At both breeding seasons five lakes contained near 85% of the population. We only observed 6 breeding colonies, two in 2009/2010 and four in 2010/2011, totalling 242 nesting attempts. Nearly 90% of the nests failed during egg stage, mainly due to strong winds and depredation by American mink Neovison vison. Only 28 nests hatched chicks, but none of the young survived to independence due to low temperatures. We compared the results of our 2010/2011 survey with one conducted during 1984/1985 and detected that the population diminished by approximately 80%. This decline was observed on all but one plateau (“Buenos Aires”) where most breeding attempts occurred. Our results show that at present Hooded Grebes are highly dependent on a few suitable lakes where they congregate to breed. We analyse possible causes for the decline of the population and propose conservation actions to protect this species.

Pup numbers of the Australian sea lion (Neophoca cinerea) at The Pages Islands, South Australia, over two decades

2013 ◽  
Vol 61 (2) ◽  
pp. 112 ◽  
Author(s):  
Peter D. Shaughnessy ◽  
Simon D. Goldsworthy ◽  
Paul Burch ◽  
Terry E. Dennis
Keyword(s):  
Population Size ◽  
South Australia ◽  
Sea Lion ◽  
Breeding Colony ◽  
Sea Lions ◽  
Neophoca Cinerea ◽  
Australian Sea Lion ◽  
Gill Net ◽  
Low Levels ◽  
Breeding Seasons

The Australian sea lion is an Australian endemic, restricted to South Australia and Western Australia, with 86% of the population in South Australia. It was listed under the Commonwealth Environment Protection and Biodiversity Conservation Act as Vulnerable in February 2005, and the International Union for the Conservation of Nature has listed it as Endangered. Sea lions are taken as bycatch in the gill-net fishery for school shark and gummy shark, and the risk of extinction of breeding colonies is high even from low levels of bycatch. We assessed trends in pup population size at The Pages Islands, a large breeding colony in South Australia. Pup abundance was estimated by direct counting of live and dead pups; the maximum count in each breeding season was used for trend analysis. The average of direct counts of pups in 14 breeding seasons between 1989–90 and 2009–10 was 473 (s.d. = 58.4). There was no trend in pup numbers, contrasting with two other large colonies: Seal Bay, Kangaroo Island (decreasing), and Dangerous Reef (increasing since 2000). The Australian Sea Lion Management Strategy of the Australian Fisheries Management Authority aims to reduce sea lion bycatch in the shark fishery; a key item is a fishery closure around each breeding colony in South Australia. Implementation of the closure around The Pages should lower the risk of bycatch of its sea lions with foraging areas that previously overlapped with the fishery and should allow the colony’s population size to increase.

Australian And New Zealand Fur Seals At The Skerries, Victoria: Recovery Of A Breeding Colony

2002 ◽  
Vol 24 (1) ◽  
pp. 57 ◽  
Author(s):  
CL Littnan ◽  
AT Mitchell
Keyword(s):  
New Zealand ◽  
Population Size ◽  
Arithmetic Mean ◽  
Aerial Photographs ◽  
Population Estimates ◽  
Breeding Colony ◽  
Mark Recapture ◽  
Aerial Surveys ◽  
Fur Seals ◽  
Breeding Seasons

The population size of Australian fur seals Arctocephalus pusillus doriferus and New Zealand fur seals A. forsteri at The Skerries, Victoria was estimated in two consecutive breeding seasons, 1999-2000 and 2000-2001 using both mark-recapture procedures and aerial surveys. 675 and 746 A. p. doriferus pups and 37 and 47 A. forsteri pups were captured and marked in 1999-2000 and 2000-2001, respectively. Resights (1999-2000 N = 3; 2000-2001 N = 6) were conducted 2 - 3 days after marking and pup population estimates were calculated using a modified Lincoln-Petersen estimate. The arithmetic mean for A. p. doriferus pup abundance was 1,867 in the first season and 2,237 in the second. A. forsteri abundance was 75 and 78, respectively. The A. p. doriferus population is estimated to have increased an average of 19.7% (r = 0.18) between 1999 and 2000. The arithmetic mean from five counts of aerial photographs of total animals present at the colony was 1,758 in 1999-2000 and 2,965 in 2000-2001. Due to high variation between counts, aerial surveys proved to be an inconsistent and inaccurate method for estimating the population of fur seals at The Skerries.

Polygamy and low effective population size in a captive Murray cod (Maccullochella peelii peelii) population: genetic implications for wild restocking programs

2009 ◽  
Vol 60 (8) ◽  
pp. 873 ◽  
Author(s):  
Meaghan L. Rourke ◽  
Helen C. McPartlan ◽  
Brett A. Ingram ◽  
Andrea C. Taylor
Keyword(s):  
Population Size ◽  
Effective Population Size ◽  
Allelic Richness ◽  
Wild Populations ◽  
Effective Population ◽  
Census Size ◽  
Common Response ◽  
In Captivity ◽  
Murray Cod ◽  
Breeding Seasons

Stocking of freshwater fish species with hatchery-bred fish is a common response to depleted wild stocks, but may have numerous genetic implications. Murray cod, Maccullochella peelii peelii (Mitchell), have been produced in captivity for wild stocking programs for more than 30 years. The potential genetic impacts of this stocking program on wild populations was investigated by using eight microsatellite markers to determine the parentage of 1380 offspring from 46 separate spawnings collected over three consecutive breeding seasons, and by estimating the effective population size of the broodfish generation through demographic and genetic methods. Results revealed unexpected incidences of polygamous spawnings (both polygyny and polyandry), multiple spawnings by both sexes within a season and repeated matings between pairs of fish across multiple seasons. Furthermore, approximately half of the broodfish failed to spawn at all over the 3-year study period. This likely contributed to the estimated effective population size of around half of the census size, moderate but significant reductions in allelic richness in all three cohorts investigated and a small but significant reduction in heterozygosity in two cohorts. These results allowed us to make recommendations regarding captive husbandry that will maximise genetic diversity of fish intended for stocking.

The superpopulation approach for estimating the population size of 'prolonged' breeding amphibians: Examples from Europe

2011 ◽  
Vol 32 (3) ◽  
pp. 323-332 ◽  
Author(s):  
Jérôme Pellet ◽  
Benedikt R. Schmidt ◽  
Norman Wagner ◽  
Stefan Lötters ◽  
Thomas Schmitt
Keyword(s):  
Population Size ◽  
Sampling Site ◽  
Amphibian Species ◽  
Breeding Sites ◽  
Open Population ◽  
Population Size Estimates ◽  
Detection Probabilities ◽  
Breeding Seasons ◽  
Population Counts ◽  
Size Estimates

AbstractIndividual members of a population of 'prolonged' breeding amphibian species are asynchronously present at their breeding sites. Therefore, population size estimates can be misleading when based on commonly used closed or open-population capture-mark-recapture approaches. The superpopulation approach, a modified Jolly-Seber model, has been successfully applied in taxa other than amphibians with distinct migratory behaviour and where individuals are asynchronously present at the sampling site. In this paper, we suggest that the superpopulation approach is a useful population size estimator for 'prolonged' breeding amphibian species. Two case studies on European anurans show that superpopulation estimates are much higher than simple population counts. A simulation study showed that superpopulation estimates are unbiased but that accuracy can be low when either survival or detection probabilities (or both) are low. We recommend the superpopulation approach because it matches the natural history and phenology of amphibian species with prolonged breeding seasons.

Reduction of spermatogonia and testosterone in rat testes flown on space lab-3

1986 ◽  
Vol 44 ◽  
pp. 248-249
Author(s):  
Delbert E. Philpott ◽  
W. Sapp ◽  
C. Williams ◽  
T. Fast ◽  
J. Stevenson ◽  
...  
Keyword(s):  
Social Interaction ◽  
Social Status ◽  
Population Size ◽  
Physiological Response ◽  
Social Rank ◽  
Reproductive Function ◽  
Testicular Development ◽  
Organ Weights ◽  
Reproductive Maturation ◽  
Metabolic Activities

Space Lab 3 (SL-3) was flown on Shuttle Challenger providing an opportunity to measure the effect of spaceflight on rat testes. Cannon developed the idea that organisms react to unfavorable conditions with highly integrated metabolic activities. Selye summarized the manifestations of physiological response to nonspecific stress and he pointed out that atrophy of the gonads always occurred. Many papers have been published showing the effects of social interaction, crowding, peck order and confinement. Flickinger showed delayed testicular development in subordinate roosters influenced by group numbers, social rank and social status. Christian reported increasing population size in mice resulted in adrenal hypertrophy, inhibition of reproductive maturation and loss of reproductive function in adults. Sex organ weights also declined. Two male dogs were flown on Cosmos 110 for 22 days. Fedorova reported an increase of 30 to 70% atypical spermatozoa consisting of tail curling and/or the absence of a tail.

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