Population Cycles in Small Mammals: The Role of Age at Sexual Maturity

Oikos ◽  
1999 ◽  
Vol 86 (3) ◽  
pp. 557 ◽  
Author(s):  
Madan K. Oli ◽  
F. Stephen Dobson
Keyword(s):  
Small Mammals ◽  
Sexual Maturity ◽  
Population Cycles

scholarly journals Longitudinal Expression of Testicular TAS1R3 from Prepuberty to Sexual Maturity in Congjiang Xiang Pigs

Animals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 437
Author(s):  
Ting Gong ◽  
Weiyong Wang ◽  
Houqiang Xu ◽  
Yi Yang ◽  
Xiang Chen ◽  
...  
Keyword(s):  
Sexual Maturity ◽  
Cell Function ◽  
Expression Patterns ◽  
Taste Receptor ◽  
Receptor Type ◽  
Mrna Levels ◽  
Early Puberty ◽  
Specific Expression

Testicular expression of taste receptor type 1 subunit 3 (T1R3), a sweet/umami taste receptor, has been implicated in spermatogenesis and steroidogenesis in mice. We explored the role of testicular T1R3 in porcine postnatal development using the Congjiang Xiang pig, a rare Chinese miniature pig breed. Based on testicular weights, morphology, and testosterone levels, four key developmental stages were identified in the pig at postnatal days 15–180 (prepuberty: 30 day; early puberty: 60 day; late puberty: 90 day; sexual maturity: 120 day). During development, testicular T1R3 exhibited stage-dependent and cell-specific expression patterns. In particular, T1R3 levels increased significantly from prepuberty to puberty (p < 0.05), and expression remained high until sexual maturity (p < 0.05), similar to results for phospholipase Cβ2 (PLCβ2). The strong expressions of T1R3/PLCβ2 were observed at the cytoplasm of elongating/elongated spermatids and Leydig cells. In the eight-stage cycle of the seminiferous epithelium in pigs, T1R3/PLCβ2 levels were higher in the spermatogenic epithelium at stages II–VI than at the other stages, and the strong expressions were detected in elongating/elongated spermatids and residual bodies. The message RNA (mRNA) levels of taste receptor type 1 subunit 1 (T1R1) in the testis showed a similar trend to levels of T1R3. These data indicate a possible role of T1R3 in the regulation of spermatid differentiation and Leydig cell function.

Small Mammals as Predators of Sawflies

1955 ◽  
Vol 87 (3) ◽  
pp. 121-123 ◽  
Author(s):  
C. H. Buckner
Keyword(s):  
Small Mammals ◽  
Biological Control Agent ◽  
Control Agent ◽  
Moderate Risk ◽  
Neodiprion Abietis ◽  
Ample Opportunity ◽  
Pristiphora Erichsonii ◽  
Mammalian Predators ◽  
One Year

The greatest predatory effect of small mammals is exerted upon insects that spend a portion of their life cycle on the ground or in the soil. Sawflies afford ample opportunity for mammalian predation, since they drop to the ground as mature larvae and spin cocoons in the soil. Such sawflies as Neodiprion abietis Harr., which remain within the cocoon for about three weeks, undergo only moderate risk of being preyed upon by small mammal. However, Pristiphora erichsonii (Htg.) remains within the cocoon from about mid-August until the following June, or even over more than one year, thus greatly extending the vulnerable period. Earlier investigations suggest that small mammals may comprise the largest single biological control agent acting against this insect (Graham 1928, Lejeune 1951), but the exact role of mammalian predators of forest insects has yet to be established.

Role of small mammals in the persistence of Louping-ill virus: field survey and tick co-feeding studies

2000 ◽  
Vol 14 (3) ◽  
pp. 277-282 ◽  
Author(s):  
L. Gilbert ◽  
L. D. Jones ◽  
P. J. Hudson ◽  
E. A. Gould ◽  
H. W. Reid
Keyword(s):  
Small Mammals ◽  
Field Survey ◽  
Louping Ill

scholarly journals DOMINANCE AND EPISTASIS IN HETEROSIS OF WHITE LEGHORN STRAIN CROSSES

1987 ◽  
Vol 67 (3) ◽  
pp. 663-680 ◽  
Author(s):  
R. W. FAIRFULL ◽  
R. S. GOWE ◽  
J. NAGAI
Keyword(s):  
Body Weight ◽  
Sexual Maturity ◽  
Egg Production ◽  
Significant Contribution ◽  
Production Traits ◽  
White Leghorn ◽  
Cross Combination ◽  
Commercial Strain ◽  
Better Than

Four unrelated pure strains of White Leghorns including a grandparent strain from industry and 12 two-strain, 24 three-strain, 24 four-strain and 12 F2 strain crosses produced contemporaneously were used to examine the role of dominance and epistasis in heterosis. A control strain and a commercial strain were also included. For egg weight, the heterosis observed closely approximated that expected due to dominance alone. For sexual maturity and body weight, dominance was the major component of heterosis, but epistasis made a significant contribution — additive by additive (A × A) genetic effects for sexual maturity and 140-d body weight, and parental epistasis for mature body weight. Both dominance and epistasis played a significant role in heterosis for egg production traits. A × A, dominance by dominance (D × D) and additive by dominance (A × D) epistasis were all important for hen-housed egg production and hen-housed egg yield. For hen-day rate of egg production, A × A epistasis was significant only early in the laying year (to 273 d), A × D and D × D were significant to 385 d and in the full year (to 497 d); however, none (A × A, A × D and D × D) was significant near the end of lay (386–497 d). Overall heterosis estimates for full year egg production measured as hen-housed egg production to 497 d or hen-day rate from housing to 497 d clearly showed that on average two-strain crosses were superior to three-strain crosses which were superior to four-strain crosses which in turn exceeded the F2 crosses. Nevertheless, several three-strain crosses had performance for egg production that was equal to or better than the two-strain cross with the highest egg production. Thus, in commerce, where the level of egg production is of great economic importance, the testing and use of a specific three-way cross combination will usually result in a better commercial product. Key words: Heterosis, egg production genetics, epistasis, stocking rate, strain cross, White Leghorn

Ticks on small mammals from an ecotone region impacted by rural activities in Brazil

2021 ◽  
Vol 26 (2) ◽  
pp. 427-437
Author(s):  
Rafael Quirino Moreira ◽  
Vanessa Do Nascimento Ramos ◽  
Adriane Suzin ◽  
Diego Garcia Ramirez ◽  
Paulo Ricardo De Oliveira Roth ◽  
...  
Keyword(s):  
Atlantic Forest ◽  
Small Mammals ◽  
Mus Musculus ◽  
Tick Species ◽  
Rattus Rattus ◽  
Riparian Forests ◽  
Forest Fragments ◽  
Cerrado Biome ◽  
Didelphis Albiventris

We evaluated the role of communities of small mammals from three distinct areas in a region of Cerrado mixed with Atlantic Forest remains for maintenance of tick fauna. Thirty-nine marsupials (Gracilinanus agilis, n = 34; Marmosa paraguaiana, n = 4; Didelphis albiventris, n = 1) and 33 rodents (Oecomys cleberi, n = 10; Nectomys squamipes, n = 4; Calomys tener, n = 4; Hylaeamys megacephalus, n = 4; Akodon sp., n = 3; Rattus rattus, n = 3; Cerradomys subflavus, n = 2; Mus musculus, n = 2; Rhipidomys macrurus, n = 1) were captured. Solely G. agilis and the four rodent species (N. squamipes, R. macrurus, C. subflavus and Akodon sp.) were infested. Four tick species were collected (Amblyomma dubitatum, Amblyomma sculptum, Ixodes loricatus and Ornithodoros mimon). A. dubitatum was the most abundant tick species on hosts. Capture success was higher in the dry season, but the infestation was similar in both seasons. Forested habitats, particularly riparian forests, resulted in higher number of hosts and ticks collected (from hosts and from vegetation), compared to pastures and anthropized sites. The association between C. subflavus and I. loricatus and between A. dubitatum and N. squamipes observed here is the first recorded in Cerrado biome. Areas with more patches of forest, including the Atlantic Forest fragments, tend to present a richest community of small mammals and associated ticks.

The relation of body size of male humpback whales to their social roles on the Hawaiian winter grounds

2002 ◽  
Vol 80 (11) ◽  
pp. 1938-1947 ◽  
Author(s):  
Scott S Spitz ◽  
Louis M Herman ◽  
Adam A Pack ◽  
Mark H Deakos
Keyword(s):  
Body Size ◽  
Sexual Maturity ◽  
Social Roles ◽  
Male Partner ◽  
Humpback Whales ◽  
Male Partners ◽  
The Social ◽  
Reproductive Unit ◽  
Significant Size

We examined the relation of body length of male humpback whales (Megaptera novaeangliae) to the social roles they adopted on the Hawaiian winter grounds: principal escort in a competitive group, secondary escort, lone escort to a mother–calf pair, male partner in a dyad, and singer. Using underwater videogrammetry, we measured body lengths of 17 principal escorts, 68 secondary escorts, 40 single escorts, 17 male partners, and 8 singers. Results revealed that (i) principal escorts were, on average, significantly larger than males in each of the remaining social roles except singer, (ii) singers were significantly larger than male partners, (iii) there were no significant size differences among secondary escorts, single escorts, or male partners. Further, principal escorts tended to be the largest or second-largest male within their individual competitive group. All principal escorts were of sizes that indicated a 0.81 probability or better of sexual maturity, based on whaling data. In comparison, more than half of the male partners, almost one-third of the secondary escorts, and one-fifth of the single escorts were of sizes that indicated a 0.5 probability or less of sexual maturity. Seven of the eight singers had a 0.9 probability or better of sexual maturity and the eighth singer a 0.5 probability. However, the data for singers are too few to allow firm conclusions to be reached about the relation of body size to singing. Overall, our findings suggest that body size confers an advantage in physical competition between male humpback whales, and that a large proportion of males adopting the role of secondary escort, single escort, and partner are likely to be sexually immature. Additionally, the competitive group appears to be a major reproductive unit in terms of bringing together a receptive female and potential mates.

scholarly journals Testing predator - prey theory by studying fluctuating populations of small mammals.

1995 ◽  
Vol 22 (1) ◽  
pp. 89 ◽  
Author(s):  
S. Boutin
Keyword(s):  
Population Dynamics ◽  
Small Mammals ◽  
Limit Cycles ◽  
Functional Responses ◽  
Predator Satiation ◽  
Linear Type ◽  
Small Component ◽  
Wide Range ◽  
Fluctuating Populations

Fluctuating populations of small mammals provide an excellent opportunity to study the functional and numerical responses of predators because of the wide range in prey density that occurs. I reinterpret data from six studies that have examined the role of predation in the population dynamics of voles in California, southern Sweden and western Finland, of snowshoe hares in northern Canada, and of house mice and rabbits in Australia. Most studies have measured functional responses by relying on changes in diet as reflected by scat or stomach contents. These methods are probably biased toward showing predator satiation. Contrary to previous conclusions I find that there is little evidence for non-linear (Type 111) functional-response curves or predator satiation at high prey densities. Recent studies indicate that the functional and numerical responses of predators can be rapid and strong enough to initiate cyclic declines, dampen fluctuations, or even cause stable numbers. The exception to this appears to be the irruptions of mice and rabbits in Australia. I propose a general explanation for the role of predation whereby the effect of predation is largely dependent on the entire prey community. When potentially cyclic prey are a small component of the overall prey biomass, generalist predators are able to prevent fluctuations by strong functional or numerical responses. As the prey community becomes dominated by a few species that fluctuate, limit cycles predominate. Limit cycles turn into irruptive population dynamics when seasonal prey reproduction is eliminated because of extended periods of vegetation growth (vegetation flushes following drought). In the future we must test assumptions underlying the way we study predation by telemetric monitoring of prey mortality and by experimentally manipulating predation.

The role of small mammals and birds in transport of matter through the shore zone of lakes

Hydrobiologia ◽  
1993 ◽  
Vol 251 (1-3) ◽  
pp. 81-93 ◽  
Author(s):  
Kazimierz A. Dobrowolski ◽  
Anna Kozakiewicz ◽  
Barbara Leźnicka
Keyword(s):  
Small Mammals ◽  
Shore Zone

scholarly journals Spatial Ecology of Small Mammals in North-central Chile: Role of Precipitation and Refuges

2007 ◽  
Vol 88 (6) ◽  
pp. 1532-1538 ◽  
Author(s):  
W. Bryan Milstead ◽  
Peter L. Meserve ◽  
Andrea Campanella ◽  
M. Andrea Previtali ◽  
Douglas A. Kelt ◽  
...  
Keyword(s):  
Small Mammals ◽  
Spatial Ecology ◽  
North Central ◽  
Central Chile
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