Female Clutch Research Articles

Optimal Reproductive Allocation in Female Dusky Salamanders: A Quantitative Test

Analyzing a model of reproduction in Desmognathus ochrophaeus using optimal-control theory suggests that female salamanders can maximize their fecundity by using one of two allocation schemes. Fecundity will be maximized either by allocating food resources to reproduction for the entire period before egg laying or, if enough food is available, by growing first and then switching to egg production later in the season. Egg mortality is minimized if the female provides maternal care at the maximum level throughout brooding. Numerical analyses using data from studies of the energetics, behavior, and demography of D. ochrophaeus indicate that the food intake of sexually mature females probably is not sufficiently high to allow growth before egg production. Furthermore, reproductive success depends on the relationship between female size, efficacy of maternal care, and predation risk. Egg clutches of small females may be subject to high mortality in spite of maternal care. Thus, energetics, behavior, and the consequences of body size may have resulted in the evolution of delayed maturity in this species.

Physiological and Environmental Sources of Variation in Reproduction: Prairie Lizards in a Food Rich Environment

Between-year variation in the reproduction of the iguanid lizards, Holbrookia maculata and Sceloporus undulatus, was studied in Nebraska during 1978 and 1981-1983. Reproduction of both species varied significantly between years but the nature of variation was different for the two species. Clutch frequency of H. maculata did not vary among years and clutch size varied only in older females (' 2 yr). Both clutch frequency and clutch size of S. undulatus varied among years. Clutch frequency varied from 1-3 for yearlings and 2-3 for older females. The size of the first clutch of older females varied significantly among years, but differences were not significant when adjusted for body length. Several physiological and environmental factors contributed to variation in reproduction. These factors included lipid storage prior to reproduction, body mass, body length, water stress, and environmental temperatures, but not food abundance during the reproductive season. The effect of each factor was dependent on the age and species of lizard as well as the stage within the reproductive cycle.

Genetic variation in egg dimensions in natural populations of the Great Tit

Length and breadth of eggs were measured in ringed populations of the Great Tit. During a part of the study volume and weight were also measured, but this did not give additional information, viz. variation in specific weight of fresh eggs and deviations from calculated volume were within the limits of precision. Only in small eggs are length and breadth positively correlated.In two populations, a major part (60–80%) of the variation in the clutch means of egg length, egg breadth, shape index and egg volume is only found between clutches of different females. The absence of correlation between different female partners of one male and the similarity of female repeatability to heritability estimates based on daughter-mother regression lead to the conclusion that 60–80% of the variation in egg dimensions is genetic.The implications for a potential rapid response to selection resulting in a micro-evolutionary change are discussed.

The energetic costs of tail autotomy to reproduction in the lizard Coleonyx brevis (Sauria: Gekkonidae).

Energy reserve utilization and energy budgets were compared in tailed and tailless adult female Coleonyx brevis. Carcass, fat body and caudal energy reserves were used for vitellogenesis; mass and energy content (cal/mg and/or cal/reserve) of each were significantly lower at oviposition than at the initiation of vitellogenesis. Total energy reserves accounted for 53% of the reproductive energy investment in tailed females compared to 29% in tailless females. Tailed females had over twice as many reserve calories for egg production than tailless females. Caudal energy reserves represented 60% of the total reserves of tailed females and were one-third greater than the total energy reserves of tailless females. To produce a clutch of eggs both tailed and tailless females supplemented energy reserves with net metabolizable energy that was available after metabolic costs were paid. Tailless females had a significantly greater rate of food ingestion and more net metabolizable energy available for reproduction than tailed females, yet allocated significantly fewer calories/day to reproduction than tailed females, primarily because of the loss of caudal reserves. Reproductive efforts of tailed and tailless females were equivalent. However, the loss of caudal reserves resulted in the production of eggs that were significantly lower in mass and energy content (cal/mg and cal/egg) than when caudal reserves were used. Results empirically support the hypothesis that reproduction has energetic priority over tail regeneration in short-lived, iteroparous species with a low probability of future reproductive success.

Reproduction and Growth of the Mud Turtle, Kinosteron subrubrum (Reptilia, Testudines, Kinosternidae), in Arkansas

Female Arkansas mud turtle (Kinosteron subrubrum) mature between their sixth and eighth winters at a plastron length of 75 to 80 mm. Vitellogenesis apparently begins in early fall and continues until the following nesting season. Ovulation and oviposition occur at least from early May through June and probably from early April to Mid-July. During this period yolked follicles continue to mature, replacing those ovulated. Egg size is not correlated with female plastron length or clutch size. Incubation period averages 106 days. Clutch size ranges from one to six, the mode being three, and is positively correlated with female plastron length. At least three clutches are laid each year. * * *

Adaptations of Polygynous Breeding in the Bobolink,Dolichonyx oryzivorus

In some species of polygynous songbirds, males assist in feeding nestlings of their first (primary) female but ignore offspring of subsequent (secondary) mates. A number of adaptations important in minimizing the disadvantages of a secondary status in female Bobolinks ( Dolichonyx oryzivorus ) have been discovered. In Bobolinks, clutches of secondary females are significantly smaller than those of primary females, thereby adjusting brood size to correspond better with food delivery capabilities of secondary hens. Commencement of incubation with deposition of the penultimate egg allows additional brood size adjustment, for the resulting hatching asynchronism promotes efficient culling of the late-hatching chick in times of food shortage, without endangering the entire brood. Secondary females differ from primary pairs in food exploitation techniques by capitalizing on insects found close to the nest and by showing less discrimination in food selection. Such behavior permits compensation in the rate of food delivery trips to secondary nestlings so as to equal the tempo maintained by both members of the primary pair, yet results in quantitative disparities in food brought to primary and secondary nestlings. Flexibility in male feeding responses, resulting in partial male assistance at secondary nests in situations where secondary brood size is exceptionally large, is also important in helping to maximize the reproductive performance of birds engaging in this mating strategy.

Reproductive Ecology of a West Texas Population of the Greater Earless Lizard, Cophosaurus texanus

The reproductive cycle of Cophosaurus texanus, in the vicinity of San Angelo, Texas, was determined from examination of 220 females and 105 males. Reproduction begins in early April and ceases by mid-August. Females mature in a single year at approximately 50 mm snout-to-vent length. Older females begin reproduction earlier and lay a larger first clutch and produce larger eggs than females just maturing. The smaller eggs of the first clutch of younger females are attributed to the lack of adequate fat storage. Approximately three clutches of six eggs each are laid by each female during 1 rep,roductive season.

Reproductive Behavior of the Chorus Frog, Pseudacris Nigrita

The reproductive behavior of Pseudacris nigrita consists of the following events. Sexually mature males migrate to the breeding areas and vocalize. Mature females move to the breeding areas and each responds to the calls of a male by moving into bodily contact with him. The male clasps the female and retains his hold if the female has the proper size, girth, behavior, etc. The female remains quiescent for 1-2 minutes. She is positively phototactic and moves to more open, usually deeper, water. Later, conspicuous abdominal contractions sweep over the female and now she is no longer positively phototactic. The female clutches onto twigs or other vegetation in the water with her forelegs and stiffly arches her body backward. Oviposition and sperm deposition occur.