Age-specific fertility rates of the Jeju pony (<Emphasis Type="Italic"> Equus caballus</Emphasis>)

Age-specific fertility is an essential parameter of life history. Here we report age-specific fertility rates, measured as the number of foals per mare per year, for Jeju ponies aged 2–28 years. The total sample consisted of 545 foals produced by 178 mares from 1988 to 2002. The mean fertility rate across all ages of the mares was 0.65 foals/mare per year (±0.24 SD). The fertility rates were above average for the 7- to 8- and 19- to 20-year-old mares, whereas they were relatively low for mares under 4 years old. The fertility rates tended to increase with the age of the stallion, but the relationship was not significant (n =15, P =0.09). The incidence of inter-birth interval was not associated with the age that the mare first reproduced (n =64 mares, P =0.99). However, mares that reproduced later in life tended to have a reduced fertility rate due to an increase in the duration of inter-birth intervals relative to mares that reproduced earlier (n =4 years of first reproduction, P =0.068). The fertility rates of Jeju ponies were lower than for other horses, perhaps because only one stallion was introduced to a relatively large herd every year. We suggest that the introduction of more stallions to the herd each year would increase fertility rates.     

Behavioral ecology of the Jeju pony (<Emphasis Type="Italic">Equus caballus</Emphasis>): Effects of maternal age,maternal dominance hierarchy and foal age on mare aggression

On Jeju Island, Korea, dominance hierarchy and maternal care according to maternal age were studied in a herd of Jeju ponies (Equus caballus), consisting of 73 mares, their foals and one stallion. Dominance ranks were nearly linear and increased significantly with the age of mares. Most aggressive encounters involved mares under 5years old. Mares under the age of 5years have apparently not established their rank. The mean frequency of aggressive actions of mares per hour increased significantly as the day of parturition approached. Aggressive actions of mares with foals decreased significantly as their foals aged. The overall frequency of aggression of mares with foals also decreased significantly with the age of the mares. Our results suggest that the cost of maternal care is lower for older, more dominant mares than for subordinate ones.     

Intestinal ciliate composition found in the feces of the Turk rahvan horse Equus caballus, Linnaeus 1758

Species composition and distribution of large intestinal ciliates were investigated in the feces from 15 Turk rahvan horses, living in the vicinity of Izmir, Turkey. Twenty-two ciliate genera consisting of 36 species were identified. This is the first report on intestinal ciliates in Turk rahvan horses and no previously unknown species were observed. The mean number of ciliates was 14.2 ± 13.9 × 10⁴ cells ml⁻¹ of feces and the mean number of ciliate species per host was 9.9 ± 7.1. No ciliates were observed in 2 horses. Bundleia and Blepharocorys were considered to be the major genera since these ciliates were constantly found in high proportions. In contrast, Paraisotricha, Didesmis and Gassovskiella were only observed at low frequencies. The ciliates found in this survey had almost the same characteristics as those described in previous reports, suggesting that there was no significant geographic variation in the intestinal ciliate fauna of equids.     

Repeated matings offset costs of reproduction in female crickets

Summary Courtship food gifts can be a significant source of nutrition to females and costly for males to produce; hence, costs of reproduction should be reduced for multiple-mating females and increased for multiplemating males in a gift-giving species. We tested this hypothesis by experimentally manipulating mating opportunities of males and females of two cricket species,Gryllodes sigillatus, a gift-giving species andGryllus veletis, a non-gift-giving species. Females of both species consume the externally attached spermatophore after mating, but inG. sigillatus, the sperm-containing ampulla is accompanied by a large gelatinous spermatophylax. In both species, survival of mated females given limited access to males was reduced relative to virgin females, thus suggesting a cost of reproduction to females. However, females given unlimited mating opportunities lived as long as virgins and also produced significantly more offspring than limited-access females. These results suggest that benefits of repeated matings, particularly those arising through spermatophore consumption, offset costs of reproduction in females. Lack of a treatment by species interaction suggests that females of both species derive nutritional benefits through spermatophore consumption, and that any additional advantage to the consumption of the spermatophylax inG. sigillatus is offset by more frequent mating byG. veletis females. In contrast to females, varying mating opportunities had no effect on male survival, suggesting that mating effort is not very costly to males. Male survival increased linearly with body mass but only when males were food-deprived, suggesting that larger males possess greater initial energy reserves to sustain their longevity when food-stressed.     

Heavy metals modify costs of reproduction and clonal growth in the stoloniferous herb Potentilla anserina

We examined costs of sexual reproduction and clonal propagation, and their consequences for resource allocation in the clonal stoloniferous herb, Potentilla anserina, a typical pioneer species in disturbed areas. We used heavy-metal treatment in soil to create unfavourable growing conditions, because costs of reproduction are more likely to be expressed when resources are limited. We also studied whether heavy metals affect the plasticity of clonal growth form that enables the plants to avoid poor growing conditions. Ramets collected from field were grown in a greenhouse under the heavy-metal treatment consisting of a control and two levels of heavy-metals added in soil. Clonal propagation was costly in terms of total biomass of flowering ramets. Also the costs of sexual reproduction were detected in flowering ramets. Contrary to our predictions, the costs of flower production were visible in the control but not in the heavy-metal contaminated plants. Only the flowering ramets were able to produce longer stolons under heavy-metal stress, but the stolon biomass was not affected by heavy metals. Results indicate that clonal propagation and sexual reproduction may be costly for P. anserina. However, the costs are modified by heavy-metal contamination.Co-ordinating editor: J. Tuomi     

Manipulation of egg production reveals costs of reproduction in the tree lizard (Urosaurus ornatus)

Life-history theory predicts that the allocation of energy to current reproduction is associated with a decrement in future fecundity, future survival, or both. I treated this notion as the cost hypothesis, and tested the assumption that current reproduction exacts a cost in future survival and fecundity. Surgical manipulations of egg production were applied to natural populations of the tree lizard, Urosaurus ornatus, in south western New Mexico by yolkectomy surgery in two different years. I reduced the number of eggs produced in the first clutch during vitellogenesis by approximately 50% in yolkectomized females relative to controls. Subsequent survival, fecundity, and growth of females were followed for two or three years, depending on the cohort. Treated females in both cohorts showed significantly higher growth and survivorship throughout the experiment than in controls. After 2 years, yolkectomized females had grown an additional 2 mm (snout-vent length) compared to controls, enough for them to add on average an additional egg to their next clutch. This demonstrated a cost in terms of future fecundity through a reduction in growth and an increase in mortality in these lizards.     

Age at first reproduction in philopatric female muriquis (<Emphasis Type="Italic">Brachyteles arachnoides hypoxanthus</Emphasis>)

Female northern muriquis (Brachyteles arachnoides hypoxanthus or B. hypoxanthus) at the Estação Biológica de Caratinga/RPPN-FMA, Minas Gerais, Brazil typically disperse from their natal groups at an average age of 6.1±0.6 years (median =6.0 years, range =5.3–7.8 years, n =22), prior to the onset of puberty and sexual activity. Immigrants do not conceive until at least their second mating season, and the minimum interval from immigration to first reproduction has been 2.0 years. Age at first reproduction in dispersing females, previously estimated at 8.9 years, has now been documented at 9.0 and 9.25 years for two females whose birth dates are known. This is older than the 7.5 years at which the only female previously known to have reproduced in her natal group gave birth. Here, we present new data from a second female that reproduced in her natal group. This female (BA) was first observed to copulate at 5.5 years, and gave birth to her first infant at 7.25 years of age. Her 1.75-year cycling-to-first conception delay was only slightly shorter than the minimum recorded for immigrant females, and thus was not responsible for her young age at first reproduction compared to dispersing females. Although our sample size is small, our findings suggest that early puberty may permit females to reproduce in their natal group, implying a possible link between life history trade-offs and dispersal patterns. Because the only two females that have reproduced in their natal group were maternal sisters, it is also possible that maternal effects on age at puberty can impact dispersal patterns, particularly in small populations of primates.     

Weight loss,reproductive output,and the cost of reproduction in the common frog,Rana temporaria

Summary The consequences of reproduction for body weight, growth and survival were studied in a Swiss population of the explosive breeder, Rana temporaria. Males and females continuously loss weight in the range of 0.5% of total body weight per day from the breeding migration throughout May. Females also lost about 33% (1983) and 29% (1984) due to spawning. In addition to this significant year-to-year variation, there was also considerable individual variation in reproductive output. Skeletochronological techniques indicated that breeding male or female frogs experienced a growth reduction of several millimeters relative to non-breeding frogs of the same body size. There was no relationship between an individual female's reproductive output in consecutive years or with her subsequent growth or survival. It was concluded that weight loss is caused by a seasonally elevated metabolism in combination with a lack of feeding and represents a basic energetic cost of reproduction, resulting in lowered growth. Individual variation in relative reproductive output is mostly environmentally induced and is not an expression of different reproductive strategies. This may explain the lack of trade-offs that are predicted by the cost-of-reproduction-hypothesis.     

Development, survival and reproduction of Euseius finlandicus (Acari: Phytoseiidae) at different constant temperatures

Development, survival and reproduction of Euseius finlandicus Oudemans were studied at seven constant temperatures (15, 20, 25, 27, 30, 32 and 34°C) in the laboratory. Within the temperature range tested, developmental period from egg to adult varied from 148 to 360.5h and 133.7 to 336.5h for females and males, respectively. The lower thermal threshold for immature development for females and males was 8.9 and 6.4°C, respectively. Survival during immature development exceeded 90% at all the temperatures from 15 to 32°C, but at 34°C an abrupt decline was recorded. Female longevity decreased gradually from 82.7d at 15°C to 12.2 d at 34°C. The mean generation time ranged from 44.3d at 15°C to 15.9d at 32°C. The highest r _m value (0.2817) was obtained at 30°C and the lowest at 15°C (0.0976). Temperatures above 30°C had an adverse effect on population increase.     

Longitudinal patterns of reproduction in wild female siamang (Hylobates syndactylus) and white-handed gibbons (Hylobates lar)

I present the 6- year reproductive histories of three wild female siamang (Hylobates syndactylus)and four white-handed gibbons (Hylobates lar)at the Ketambe Research Station (Sumatra, Indonesia). Reproductive output varied considerably among females. Two females failed to gestate: both were nulliparous young adult H. lar,one of which remained unpaired for 4 years after dispersing from her group, while the other lost her recently acquired mate to another female. Only one- (a white-handed gibbon)- gave birth more than once, yielding interbirth intervals of 22 and 31 months. Pair bond stability or reduced interspecific feeding competition or both factors may have contributed to the brevity of these intervals. The other females- one H. lar,and three H. syndactylus-each gave birth once, suggesting minimum interbirth intervals exceeding 4–5 years (H. lar)and 3 years (H. syndactylus)in these individuals. Even given the pronounced variation observed among H. lar,these data suggest that interbirth intervals may often exceed the 2- to 3- year interval commonly attributed to these two species. Sources of reproductive failure were 1) maternal abandonment of the neonate due to impaired ability to provide maternal care (H. syndactylus,),(2) premature or stillbirth (H. syndactylus,),and (3) pregnancy termination (H. lar).These data and a review of information on longevity and age at menarche suggest that the actual lifetime reproductive output of a siamang or white-handed gibbon female may often fall far short of the 10 offspring/lifetime originally proposed for these species. Indeed, females may rear as few as five offspring to weaning in a lifetime, which is a figure reminiscent of the reproductive potential of some pongids. Finally, variance in female reproductive success is higher than expected in these monogamous species, which suggests that females (and males) are under strong selective pressure to exert mate choice, possibly through acquisition of (new) mates and extrapair copulations. Future research must clarify the availability of opportunities for paired adults to engage in these sociosexual behaviors.     

Variation of within-day foraging costs in the striped mouse (Rhabdomys pumilio)

Foraging behavior is influenced by spatial and temporal habitat heterogeniety. Here we report on within-day foraging and perceived risk of predation by the striped mouse (Rhabdomys pumilio) in a grassland savannah with wooded “islands” using giving-up densities (GUD, amount of food left behind in depletable food patches). Higher GUDs correspond to higher forging costs. GUDs were measured six times per day at 2-h intervals from paired stations along fern–grass habitat boundaries at 3 and 6 m distances from 10 wooded islands. R. pumilio's GUDs varied significantly over the course of the day with highest GUDs during the afternoon hours of 1–3 pm, and lowest between 7 and 9 am in the morning. The same pattern was consistent for both habitats (fern and grass) and distances from the wooded islands. GUDs decreased with distance from the woody islands in both fern and grass habitats and were significantly lower in the fern habitat. This activity pattern suggests that R. pumilio responds to a spectrum of spatially and temporally varying risks from a variety of predators including aerial predators that increase risk as they make use of mid-day thermals.     

Gender-specific costs of reproduction on vegetative growth and physiological performance in the dioecious shrub Corema album

Background and Aims

Reproductive costs imply trade-offs in resource distribution at the physiological level, expressed as changes in future growth and/or reproduction. In dioecious species, females generally endure higher reproductive effort, although this is not necessarily expressed through higher somatic costs, as compensatory mechanisms may foster resource uptake during reproduction.

Methods

To assess effects of reproductive allocation on vegetative growth and physiological response in terms of costs and compensation mechanisms, a manipulative experiment of inflorescence bud removal was carried out in the sexually dimorphic species Corema album. Over two consecutive growing seasons, vegetative growth patterns, water status and photochemical efficiency were measured to evaluate gender-related differences.

Key Results

Suppression of reproductive allocation resulted in a direct reduction in somatic costs of reproduction, expressed through changes in growth variables and plant physiological status. Inflorescence bud removal was related to an increase in shoot elongation and water potential in male and female plants. The response to inflorescence bud removal showed gender-related differences that were related to the moment of maximum reproductive effort in each sexual form: flowering in males and fruiting in females. Delayed costs of reproduction were found in both water status and growth variables, showing gender-related differences in resource storage and use.

Conclusions

Results are consistent with the existence of a trade-off between reproductive and vegetative biomass, indicating that reproduction and growth depend on the same resource pool. Gender-related morphological and physiological differences arise as a response to different reproductive resource requirements. Delayed somatic costs provide evidence of gender-related differences in resource allocation and storage. Adaptive differences between genders in C. album may arise through the development of mechanisms which compensate for the cost of reproduction.     

The presence of inhibitors of the reproduction of Varroa jacobsoni Oud. (Gamasida: Varroidae) in infested cells

The mite Varroa jacobsoni was reared in artificial gelatin cells under laboratory conditions and the possible presence of factors inhibiting Varroa reproduction was studied. In cells infested with three mites, the mean offspring per female was reduced to 75% of that in singly infested cells. When gelatin cells were used for two successive rearing cycles, both the proportion of reproducing females and the offspring per reproducing female were significantly lower in cells that had contained an infested larva during the first rearing cycle than in those with an uninfested larva. The mean reduction of the offspring per female was 48%; this suggests that inhibitors of the reproduction are released into infested cells. Treatment of gelatin cells with the hexane extract of cells in which an infested bee pupa had developed caused a 21% reduction in the mean offspring per female, with a difference close to the significance level (p=0.07).     

Reproductive success and nestling diet in the Lesser Spotted Woodpecker ( Picoides minor ): the early bird gets the caterpillar

Populations of Lesser Spotted Woodpecker (Picoides minor) are decreasing in size, necessitating management strategies. However, data on the reproductive biology of this species are scarce. The aim of this study was to investigate the influence of timing of breeding and nestling diet on the reproductive success of the Lesser Spotted Woodpecker and thereby contribute to an understanding of the determinants influencing its reproductive success. During 6 study years between 1996–2003, we investigated various variables of reproductive success in a Lesser Spotted Woodpecker population in the Taunus low mountain range, Germany. We observed nestling feeding at breeding holes to assess the composition of nestling diet and how it changes during the season. Clutch size, number of fledglings as well as body mass of the nestlings declined with the start of egg laying. Pairs composed of individuals that had breed together in previous years started egg laying earlier than newly established pairs. Nestling diet consisted mainly of aphids, caterpillars, craneflies and wood-living larvae. The composition changed considerably within the breeding season in both early and late broods. However, early broods were provided with caterpillars more frequently, whereas late broods received wood-dwelling larvae more often. Our results suggest that Lesser Spotted Woodpeckers time their breeding so as to coincide with the early nestling stage with the highest availability of caterpillars, since this is the time of highest energy demand. Moreover, food availability declines during the breeding season, and the decline in reproductive performance seems to be an effect of this development.     

The role of sexual and clonal reproduction in maintaining population in Fritillaria camtschatcensis (L.) Ker-Gawl. (Liliaceae)

Fritillaria camtschatcensis can reproduce by means of both sexual reproduction and clonal multiplication. Despite prolific seed production, no seedlings have been found for several years in natural populations on Mt Hakusan. The purposes of this paper are to clarify: (i) whether population size is maintained mainly by clonal multiplication; and (ii) if this is the case, to what extent occasional seedling establishment affects population growth rate and population structure. Two permanent quadrats were placed in subalpine meadows in 1992 on Mt Hakusan. Plant size, location and reproductive states for all ramets in the quadrats were recorded every year. Projection matrices were created based on field census, and computer simulation experiments were performed. Fritillaria camtschatcensis had two types of flower, male flower and cosexual flower, and they were changeable. This is the first report on sex lability in Fritillaria. Clonal growth was more closely correlated with life-history stages, especially with sexual states than with plant size. The population growth rate, , was 1.006 for the Mizuyajiri population and 1.047 for the Nanryu population, respectively. Seedlings were found in 1996 for the first time. These facts indicate that populations of F. camtschatcensis on Mt Hakusan can usually be maintained by clonal multiplication. However, it is not yet certain whether seeds germinate every year or whether a flush of seedling emergence occurs once in every few years in natural populations. Computer simulation revealed that: (i) there was a critical germination rate above which population growth rate suddenly increased; and (ii) occasional seedling establishment could provide almost the same contribution to population growth rate as that of annual seedling establishment. These results suggest that population size can be maintained mainly by clonal multiplication, and the role of sexual reproduction lies beyond maintaining the population size in F. camtschatcensis.     

Aspects of reproduction and behavioral and vocal development in Senegal Bushbabies(Galago senegalensis)

Aspects of reproduction and development of the young in Galago senegalensiswere investigated as part of a long-term study of small groups which were housed at indoor and outdoor enclosures in southern Germany. Estrus and delivery of the young may occur in all months of the year. All of the 23 births recorded were singletons. Postpartum estrus is unusual; normally, females come into estrus 4 to 5 weeks after parturition. Gestation length was 141 ± 1.6 days measured from midestrus. Gravid females, or females with off-spring, were never separated from their family groups since the fathers and offspring from earlier litters were intensivly engaged in positive interactions with the growing young. The development of locomotion, social behavior, and vocal patterns from birth to nutritional weaning is described. Youngsters had specific vocalizations, which were, for the most part, different from those of adults. The results are compared with reproduction and behavioral ontogeny in related prosimian species.     

Observations on the morphology,reproduction and cytology of stigeoclonium pascheri (vischer) cox et bold (chaetophorales-chlorophyceae) and their bearing on the validity of the genus caespitella vischer

The present communication deals with the morphology, reproduction and cytology of Stigeoclonium pascheri (formerly described as Caespitella pascheri Vischer). Effects of various concentrations of nitrate and variations in intensity and duration of light period in 24 hr LD cycles were studied on cultures of this alga in relation to the type and extent of branching and occurrence or absence of hair formation. It is concluded that these traits are not of taxonomic significance and are influenced largely by environmental conditions. The present study shows a large overlapping of morphological characters between the genera Stigeoclonium and Caespitella and supports Cox & Bold's abandonment of the latter generic name and its merger into the genus Stigeoclonium. The chromosome number determined for this alga is n = 6 which indicates that the Indian strain of this alga is a distinct cytotype from the one originally isolated by Vischer.     

Energy allocation for reproduction in a marsupial arboreal folivore,the common ringtail possum (Pseudocheirus peregrinus)

This study examines the annual energetics of a small folivorous marsupial, Pseudocheirus peregrinus. Particular attention was given to the energy and time allocated to reproduction by the females. Daily energy expenditure was measured directly using the doubly labelled water technique. Energy transferred to the young via the milk was estimated from information on milk composition and production. There was no significant seasonal variation in the energy expenditure or water influx of males or females. The mean daily energy expenditure of a 1-kg non-lactating adult ringtail possum was 615 kJ day^–1 or 2.2 times standard metabolic rate. Females showed significant changes in daily energy expenditure according to their reproductive status. Without the burden of lactation the total annual energy expenditure of an adult female was estimated as 212.4 MJ kg^–1 year^–1. The total annual energy expenditure of a female rearing two young was 247.5 MJ kg^–1 year^–1, with the late stage of lactation constituting the most energetically expensive period accounting for 30% of the total yearly energy expenditure during 24% of the time. Total metabolisable energy allocation during reproduction (22 MJ kg) was similar to estimates available for other herbivores, although, the peak metabolisable energy allocation during lactation (759 kJ day^–1) was lower than values available for other herbivores. The total energy requirement for reproduction (metabolisable energy plus potential energy exported to young via milk) suggests that the ringtail possum also has a relatively low overall energy investment in reproduction. It is suggested that the lactational strategy of the ringtail possum has been selected in order to spread the energy demands of reproduction over time due to constraints on the rate of energy intake imposed by a leaf diet and/or to prolong the mother-young bond. The strategies a female ringtail possum may employ to achieve energy balance when faced with the energy demands of reproduction are discussed.     

Influence of feeding interval on reproduction and longevity ofPodisus sagitta (Het.: Pentatomidae)

The effect of various feeding intervals on reproduction and longevity of the predatory bugPodisus sagitta (Fabricius) (Heteroptera: Pentatomidae) was studied in the laboratory. Isolated pairs of adult bugs were given moisture in excess and were fed 1 seventh-instar larva of the greater wax moth,Galleria mellonella (L.), with a mean weight of 90 mg every 1, 3, 7, 14 and 21 days. Reproduction ofP. sagitta reflected well the feeding intervals. Females fed at increasing time intervals reduced reproductive outputs by decreasing oviposition frequency and size of egg batches. Predators fed every 21 days produced a mean of only 1.0 egg per day in comparison with 9.9 eggs per day for females fed daily. Longevity of females fed daily was 110.7 days; females fed less frequently tended to live longer, with a maximum mean longevity of 217.5 days for females fed every 14 days. No cannibalism among adults was observed, but females were occasionally seen to feed on their own eggs. Availability of moisture was found to be essential for the predators to survive during periods of low food supplies. These findings are discussed in relation to the predator's adaptation strategies in conditions of prey scarcity.      

Location,reproduction and movement of Neoseiulus californicus (Acari: Phytoseiidae) during the autumn,winter and spring in orchards in the south of France

Field samples and experiments conducted in apple orchards in the south of France showed that Neoseiulus californicus (McGregor) searched for prey on the trees and in the ground cover as late as mid-November 1993, and at least as early in the spring as the end of February 1994. Overwintering females fed, expanded and produced viable eggs within 7.9±0.3 (SE) days given the natural light regime, adequate food and temperatures of 17.0±20.6°C. The first generation of N. californicus developed in the field during March and April 1994. N. californicus nymphs, females and males readily moved over bare ground and through a grass ground cover to trap plants located on stakes 1 m above the ground. In the laboratory, the rate of movement of adult females on 0.5 mm copper wire was a linear function of temperature above a threshold of 11.9±0.9°C. At 25°C they travelled 10 m per h. The migration rate of N. californicus to trap plants on stakes placed in an orchard 13 Apr. increased in 2 weeks from 0.07 to 0.57 predators/trap plant/degree-day, while the migration rate to plants placed directly in the ground cover was 1.45 predators/trap plant/degree-day. The largest population of N. californicus in April occurred on Barley, Hordeum murinum L. This plant produces pollen in April and May, and may be useful in biocontrol programs.