Reproduction in natural populations of the red kangaroo, Megaleia rufa (Desmarest), in central Australia.

1965 ◽  
Vol 13 (5) ◽  
pp. 735 ◽  
Author(s):  
A. E. Newsome
Keyword(s):  
Drought Index ◽  
Natural Populations ◽  
Late Pregnancy ◽  
Arid Environment ◽  
Adaptive Significance ◽  
Severe Drought ◽  
Summer Drought ◽  
Red Kangaroo ◽  
Males And Females ◽  
Central Australia

Reproduction in the red kangaroo, Megaleia rufa (Desmarest), in the arid environment of central Australia is highly opportunistic, and depends on the weather through its control of the food supply for its success. This conclusion is based on the study of 460 males and 1610 females between the years 1958 and 1962. Males and females matured sexually at an average age of about 2.5 and 3 yr, respectively. Drought significantly retarded sexual maturity in females by 6.24� 1.26 months. All females bred when green herbage was abundant after good rains. However, when food was scarce during drought, many females entered anoestrus, the proportion doing so being a probit function of the severity of the drought (measured in units of "drought index" explained in the text). Half of them became anoestrous after 3-5 months of drought in summer. Drought on the more scantily grassed of the two areas studied (they were 15-20 miles apart) was 1.57 times more effective in inducing anoestrus than on the other. All pouch-young survived if good conditions held for about 8 months, but many died during drought, the proportion doing so being a probit function of the increase in severity of drought after they were born. Half of them perished after 1.5-2.5 months of drought in summer. Only 28.7% of all joeys born survived life in the pouch because of the prolonged dry weather. Pouch-young were significantly lighter, and joeys-at-heel were 13.5 � 1.9 days older during drought than at other times. The birth of twin joeys was associated with an abundance of food. During severe drought, many females showed signs of having produced in quick succession one or more joeys which did not live long. Many of these females were anoestrous and suckling a small joey. Since most if not all females which became anoestrous did so during late pregnancy without aborting and subsequently suckled their pouch-young, it is suggested that the adaptive significance of delayed implantation is to ensure that females which have lost a joey and which are about to become anoestrous produce one more joey each. These joeys will be born well into any drought and therefore will have to live for a shorter time than older joeys to survive the drought. The advantage to the species can be gauged from the fact that 50 out of 145 females with young surviving the drought were anoestrous. The ages of their joeys averaged 60.1 � 7.6 days.

Oestrus in the lactating red kangaroo.

1964 ◽  
Vol 12 (3) ◽  
pp. 315 ◽  
Author(s):  
AE Newsome
Keyword(s):  
Corpus Luteum ◽  
Reproductive Cycle ◽  
Environmental Conditions ◽  
Similar Case ◽  
Severe Drought ◽  
Reproductive Condition ◽  
Pregnant Females ◽  
Red Kangaroo ◽  
Central Australia ◽  
Poor Nutrition

The reproductive condition of 18 female red kangaroos, Megaleia rufa (Desmarest), collected in central Australia and found to be suckling sizeable pouch young (average age about 54 days), is described. They were either approaching, undergoing, or had just undergone oestrus. None had a mature corpus luteum of lactation in either ovary. No similar case was found in many hundreds of females suckling sizeable pouch young which had a mature corpus luteum of lactation in one of their ovaries. It is concluded that the presence of a functional corpus luteum of lactation or of pregnancy in the ovary may be the only inhibitor of ovulation in the mature Megaleia, provided that environmental conditions are suitable. Some kangaroos during severe drought miss the customary oestrus following birth of a young because the pregnant females do not undergo the reproductive changes necessary for it. Despite this disruption of the reproductive cycle the young are born and suckled normally, but the females cannot, therefore, have a corpus luteum of lactation. The 18 females described in this paper must have belonged to this class of animals during the drought, their condition having been brought on presumably by poor nutrition. The unusual features of reproduction in Megaleia are hard to reconcile with the assumptions that pregnancy in marsupials depends on the hormones of the normal oestrous cycle, and that reproduction in marsupials is controlled by the same kinds of hormones found in eutherian mammals; doubt is, therefore, thrown on the validity of these assumptions. Megaleia has a remarkable ability to care for its young during severe drought, and a method of overcoming the effects of the drought on its reproductive cycle when the drought breaks, with the result that the production of young is not impaired. Both these features must aid the chance of the species to survive in the arid parts of Australia.

Anoestrus in the red kangaroo Megaleia rufa (Desmarest).

1964 ◽  
Vol 12 (1) ◽  
pp. 9 ◽  
Author(s):  
AE Newsome
Keyword(s):  
Luteal Phase ◽  
Post Partum ◽  
Arid Environment ◽  
Adaptive Significance ◽  
Oestrous Cycle ◽  
Ovarian Activity ◽  
Previous Pregnancy ◽  
Quiescent Period ◽  
Red Kangaroo ◽  
Prolonged Drought

The red kangaroo, M. rufa, normally has a post-partum oestrus and a quiescent period of lactation as do some other macropod marsupials. The term "quiescent period of lactation" has been defined in this paper as the period of reproductive stasis between post-partum oestrus and the resumption of ovarian activity which follows when the female ceases, or almost ceases to suckle the young. This term is introduced to replace the term "lactation anoestrus". It has been shown that some females failed to undergo post-partum oestrus during prolonged drought, each female having entered anoestrus during the previous pregnancy; such pregnancies were not interrupted, but carried to term, and the young sometimes suckled for 3-4 months. In some other females, anoestrus set in during an unfertilized oestrous cycle. It is thought that anoestrus may result from lack of food because anoestrous females are found only during prolonged drought. The histology of the uteri of lactating anoestrous females has been described, and shown to be indistinguishable from that of the uteri of non-lactating anoestrous females, and very different from that in animals in the quiescent period of lactation. The anoestrous condition appeared in the uterus after the cessation of the luteal phase. Pregnancy is therefore independent of the oestrous cycle in Megaleia when the luteal phase has passed. The onset of anoestrus in Megaleia is compared with that in Elephantulus rupestris jamesoni Chubb, Sorex araneus (L.), Oryctolagus cuniculus (L.), Setonix brachyurus (Quoy & Gaimard), and Potorous tridactjhs (Kerr), all of which usually undergo post-partum oestrus. In Oryctolagus and Elephantulus, anoestrus may lead to the death respectively of the young and foetus. It is suggested that the milder consequences of anoestrus in Megaleia may be of adaptive significance to the species in a semi-arid environment, since the embryos and pouch-young of anoestrous females have a chance to survive drought.

scholarly journals Summer drought decreases the predictability of local extinctions in a butterfly metapopulation

2019 ◽  
Author(s):  
Erik van Bergen ◽  
Tad Dallas ◽  
Michelle F. DiLeo ◽  
Aapo Kahilainen ◽  
Anniina L. K. Mattila ◽  
...  
Keyword(s):  
Water Balance ◽  
Ecological Model ◽  
Natural Populations ◽  
Ecological Impacts ◽  
Severe Drought ◽  
Summer Drought ◽  
Population Growth Rates ◽  
Extreme Climatic Events ◽  
Local Extinctions ◽  
Spatio Temporal

ABSTRACTThe ecological impacts of extreme climatic events on population dynamics and/or community composition are profound and predominantly negative. Here, using extensive data of an ecological model system, we test whether predictions from ecological models remain robust when environmental conditions are outside the bounds of observation. First, we report a 10-fold demographic decline of the Glanville fritillary butterfly metapopulation on the Åland islands (Finland). Next, using climatic and satellite data we show that the summer of 2018 was an anomaly in terms of water balance and vegetation productivity indices across the habitats of the butterfly, and demonstrate that population growth rates are strongly associated with spatio-temporal variation in climatic water balance. Finally, we demonstrate that covariates that have previously been identified to impact the extinction probability of local populations in this system are less informative when populations are exposed to (severe) drought during the summer months. Our results highlight the unpredictable responses of natural populations to extreme climatic events.

scholarly journals No sex differences in learning in wild bumblebees

2021 ◽  
Author(s):  
Felicity Muth ◽  
Amber D Tripodi ◽  
Rene Bonilla ◽  
James P Strange ◽  
Anne S Leonard
Keyword(s):  
Sex Differences ◽  
Associative Learning ◽  
Sierra Nevada ◽  
Comparative Cognition ◽  
Natural Populations ◽  
Interspecific Variation ◽  
Learning Task ◽  
Learning Ability ◽  
Learning Performance ◽  
Males And Females

Abstract Females and males often face different sources of selection, resulting in dimorphism in morphological, physiological, and even cognitive traits. Sex differences are often studied in respect to spatial cognition, yet the different ecological roles of males and females might shape cognition in multiple ways. For example, in dietary generalist bumblebees (Bombus), the ability to learn associations is critical to female workers, who face informationally rich foraging scenarios as they collect nectar and pollen from thousands of flowers over a period of weeks to months to feed the colony. While male bumblebees likely need to learn associations as well, they only forage for themselves while searching for potential mates. It is thus less clear whether foraging males would benefit from the same associative learning performance as foraging females. In this system, as in others, cognitive performance is typically studied in lab-reared animals under captive conditions, which may not be representative of patterns in the wild. In the first test of sex and species differences in cognition using wild bumblebees, we compared the performance of Bombus vancouverensis nearcticus (formerly bifarius) and Bombus vosnesenskii of both sexes on an associative learning task at Sierra Nevada (CA) field sites. Across both species, we found that males and females did not differ in their ability to learn, although males were slower to respond to the sucrose reward. These results offer the first evidence from natural populations that male bumblebees may be equally as able to learn associations as females, supporting findings from captive colonies of commercial bees. The observed interspecific variation in learning ability opens the door to using the Bombus system to test hypotheses about comparative cognition.

scholarly journals Caucasian clover performance in a year of severe drought

1998 ◽  
pp. 119-125
Author(s):  
R.N. Watson ◽  
F.J. Neville ◽  
N.L. Bell
Keyword(s):  
White Clover ◽  
Growth Rates ◽  
Volcanic Ash ◽  
Severe Drought ◽  
Summer Drought ◽  
Volcanic Ash Soil ◽  
Summer Growth

In a year of spring-summer drought on a sandy volcanic ash soil, ryegrass/caucasian clover (RG/ CC) and RG/white clover (RG/WC) pastures had similar rapid increases in pasture growth rates during September. Growth rates peaked around 25 October (65-70 kg DM/ha/day) for RG/CC and around 14 October (50-60 kg DM/ha/day) for RG/ WC. As drought intensified the declines in pasture growth rates were similar, but delayed by up to 3 weeks for RG/CC. Both pastures reached minimum summer growth rates of

scholarly journals Population and reproductive traits of a freshwater amphipod (Crustacea, Peracarida, Hyalellidae) from northwest of the state of Rio Grande do Sul, Brazil

2020 ◽  
Vol 20 (2) ◽  
Author(s):  
Daniela da Silva Castiglioni ◽  
Marcio Limberger ◽  
Vanessa da Silva Castro ◽  
Francieli Ubessi
Keyword(s):  
No Reduction ◽  
Natural Populations ◽  
Reproductive Traits ◽  
Bimodal Distribution ◽  
Southern Brazil ◽  
Natural Pond ◽  
Males And Females ◽  
The Mean ◽  
Anthropic Influence ◽  
Almost All

Abstract The study of population and reproductive traits provides information about the ecological structure of natural populations. This study aimed to characterize dynamics and reproductive traits of Hyalella palmeirensis from a natural pond from southern Brazil. The amphipods were sampled monthly (August 2012 to July 2013) by a person with the aid of a hand net for 20 minutes. Ovigerous females and pre-copulatory pairs were individualized in the field. A total of 12,325 individuals were sampled, being 1,421 males, 6,983 females (including 215 ovigerous females) and 3,921 juveniles. Paired and unpaired males were significantly greater in size than females. There was a positive correlation between body size (CL) of paired males and females. Males and females showed bimodal distribution. Total sex ratio favored females, and these were more frequent in almost all months. Ovigerous females and precopulatory pairs were found throughout the year, but with high frequency in winter and autumn, respectively, characterizing a seasonal reproduction. Juveniles were sampled throughout the year, with greater intensity in the spring. The mean fecundity was 19.6 ± 4.34 eggs. No reduction in the number of eggs was observed during embryonic development. The results observed in H. palmeirensis demonstrate that this species has a population and reproductive dynamics very similar to other species of Hyalella already analyzed in southern Brazil. Moreover, it can be seen that although the H. palmeirensis occurs in an environment with anthropic influence (soy cultivation,) the population is managing to remain in the area, with reproduction and recruitment in most months of year.

scholarly journals Components of litter size in mice after 110 generations of selection

Reproduction ◽  
2004 ◽  
Vol 127 (5) ◽  
pp. 587-592 ◽  
Author(s):  
M Holt ◽  
O Vangen ◽  
W Farstad
Keyword(s):  
Litter Size ◽  
Late Pregnancy ◽  
Ovulation Rate ◽  
Control Line ◽  
Embryo Survival ◽  
High Line ◽  
Line Selection ◽  
Males And Females ◽  
The Mean ◽  
Standard Deviations

The aim of the present study was to evaluate how ovulation rate and survival rate through pregnancy had been affected by more than 110 generations of upwards selection on litter size in mice. The mean number of pups born alive was 22 in the high line (selected line) and 11 in the control line (an increase in 2.6 standard deviations). Selection on litter size increased ovulation rate by 4.6 standard deviations, and it is suggested that selection also increased embryonic mortality in late pregnancy. Embryo survival from ovulation until birth was 66% in the selected line and 69% in the control line, and the observed loss in litter size from day 16 of pregnancy until birth was possibly higher in the high line compared with the control line. Selection for higher litter size has significantly increased body weight in both males and females, as the mean weight at mating for the females was 46 g in the high line and 33 g in the control line respectively.

scholarly journals Ultraviolet Degradation in Carotenoid Patches: Live Versus Museum Specimens of Wood Warblers (Parulidae)

The Auk ◽  
2005 ◽  
Vol 122 (3) ◽  
pp. 793-802 ◽  
Author(s):  
Gabriel D. McNett ◽  
Karen Marchetti
Keyword(s):  
Natural Populations ◽  
Adaptive Significance ◽  
Color Variation ◽  
Museum Specimens ◽  
The Past ◽  
Wood Warblers ◽  
Color Spectrum ◽  
The Difference ◽  
Using Data ◽  
Source Materials

Abstract Accurate assessment of color is essential in testing the adaptive significance of color variation in avian plumage. Over the past decade, use of objective methods for assessing color has increased, with particular emphasis on ultraviolet (UV) wavelengths. Researchers have used various source materials, most notably museum specimens, to extend or represent color measurements of individuals in natural populations. Here, we address whether the colors seen in museum specimens accurately represent the colors seen in natural populations. We focus on UV wavelengths and carotenoid-derived colors across 10 species of wood-warblers (Parulidae). Our results indicate an uneven decrease in brightness across the color spectrum, with greater relative decrease in shorter wavelengths in museum specimens. That decrease leads to differences in both hue and chroma between living and museum specimens. The difference from live specimens appears to increase with the museum specimen's age. Our results suggest that caution is needed when using data from museum specimens to test hypotheses on plumage coloration, particularly those involving communication. Degradación Ultravioleta en Parches de Carotenoides: Especímenes Vivos versus Especímenes de Museo de Especies de la Familia Parulidae

Detection of intergenomic translocations with centromeric and noncentromeric breakpoints in Triticum araraticum: mechanism of origin and adaptive significance

Genome ◽  
1995 ◽  
Vol 38 (5) ◽  
pp. 976-981 ◽  
Author(s):  
Ekatherina D. Badaeva ◽  
Jiming Jiang ◽  
Bikram S. Gill
Keyword(s):  
Natural Populations ◽  
Chromosome Translocation ◽  
Adaptive Significance ◽  
Genomic In Situ Hybridization ◽  
Intraspecific Diversity ◽  
Wild Progenitor ◽  
Intergenomic Translocations ◽  
Species Specific ◽  
Triticum Araraticum

Triticum araraticum Jakubz. (2n = 4x = 28, AtAtGG), a wild progenitor of the polyploid cultivated wheat T. timopheevii, shows extensive chromosome translocation polymorphism in natural populations from the Middle East and Transcaucasia. From an extensive survey, eight intergenomic translocation types were observed and their breakpoints analyzed by genomic in situ hybridization. The previously reported species-specific 6At–1G–4G cyclic translocation was found in all accessions studied. In four translocation types, the breakpoints were in interstitial regions of chromosomes and the other four arose via centric–breakage–fusion. A model is presented on the mechanism of origin and the adaptive significance of translocations with centromeric and noncentromeric breakpoints.Key words: intraspecific diversity, intergenomic translocations, Triticum araraticum.

Seasonal Changes in Diet Preferences of Free-Ranging Red Kangaroos, Euros and Sheep in Western New South Wales.

1977 ◽  
Vol 4 (2) ◽  
pp. 127 ◽  
Author(s):  
BA Ellis ◽  
EM Russell ◽  
TJ Dawson ◽  
CJF Harrop
Keyword(s):  
Animal Species ◽  
New South ◽  
New South Wales ◽  
Stomach Contents ◽  
Ovis Aries ◽  
Severe Drought ◽  
Red Kangaroo ◽  
South Wales ◽  
Selective Eating ◽  
Free Ranging

Stomach contents of free-ranging animals were analysed botanically for low Atriplex shrubland in western New South Wales, Australia, during 1972-74 in good seasons producing abundant growth and diversity of vegetation. Red kangaroo (Megaleia rufa), euro (Macropus robustus) and sheep (Ovis aries) selected grass and forbs when those were readily available. In poorer pasture sheep selected mainly flat-leaved chenopods (saltbush) and kangaroos selected mainly grass with different amounts of flat- or round-leaved chenopods. Euros were the most selective, eating grass even when there was little grass present. Potential overlaps in diet between kangaroos and sheep were greatest in good pasture and least in the poorest conditions. The other groups of plants considered were non-chenopod shrubs and browse. Extent of overlap was not clear, because animals may have eaten different species within the groups of plants. The study period did not include any severe drought, in which overlap in diet and competition between animal species would have been most significant.

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