BREEDING BIOLOGY OF SOUTHERN ELEPHANT SEALS IN PATAGONIA

Abstract: Elephant seals breed in Patagonia (Península Valdés, Argentina) from late August to early November, reaching peak numbers during the first week in October. Observations of this population over the past ten years yielded similar results. Eighty percent of the pups were born by 2 October. Most (96%) of 663 females marked during three breeding seasons gave birth to a pup. Females stayed on land a mean of 28 d, gave birth 6 d after arrival, nursed their pups for 22 d, and copulated a mean of 2.5 times 20 d after parturition and 2 d before departure. Copulations peaked during the third week in October. Males spent 57–80 d on land fasting and defending harems of up to 134 females (median 11–13 females, depending on year). Most (96%) marked females that gave birth ( n = 636) also weaned their pups successfully. Pup sex ratio was unity. Harems were smaller and breeding occurred about three weeks earlier in Patagonia than in other colonies. Thermal conditions, day length and food availability may explain clines in the timing of breeding events between populations, Other parameters of the breeding season for the expanding Patagonia colony are similar to those for declining southern elephant seal populations elsewhere.     

Grey seal, Halichoerus grypus, energetics: females invest more in male offspring

Grey seal females transfer large amounts of energy to their pups during the brief lactation period. The costs of lactation have been measured using weight changes of mother and pup pairs. Large females come ashore to give birth earlier in the season and lose weight more rapidly than smaller females. The sex ratio of Grey seal pups born is skewed towards males in the early part of the breeding season. Male pups are larger at birth and gain weight more rapidly than female pups, and their mothers show a correspondingly faster rate of weight loss than mothers of female pups. The energy costs of gestation and lactation to a Grey seal mother are 31 GJ for male pups and2–8 GJ for female pups. Males are therefore 10% more costly in energy terms to raise to weaning. Because, on average, large females arrive at breeding sites before smaller animals, biased results on weight changes would be obtained from methods which do not use repeated weighings. We suggest that the high efficiencies of lactation estimated for Harp seals compared with other phocid seals could be accounted for by such a bias.     

REPRODUCTIVE CYCLE OF THE CUTTLEFISH, SEPIA OFFICINALIS (L.) IN THE NORTHERN PART OF THE BAY OF BISCAY

The sexual cycle of the cuttlefish, Sepia officinalis, fromthe northern part of the Bay of Biscay was followed over severalyears (1988 to 1990 and 1992 to 1993). Successive maturity stagesare reached at the same time regardless of site in the northernpart of the Bay. In this area, the majority of cuttlefish reproduceduring their second year of life (group II) whereas the remainderreproduce in their first year (group I). The first visible signsof sexual development concern the testis in males and the genitaltract in females. Males mature earlier than females: the firstspermatophores appear in July (group II) and October (groupI) while mature eggs appear from December (group II) and March(group I). The breeding season lasts from about mid-March tolate June (3.5 months). (Received 2 February 1996; accepted 30 May 1996)     

Seasonal and individual variation in gregarine parasite levels in the field crickets Gryllus veletis and G.pennsylvanicus

ABSTRACT. 1. Gregarines, debilitating protozoan gut parasites, were monitored in two species of field cricket, Gryllus veletis (Alexander and Bigelow) and G.pennsylvanicus Burmeister, in northern Michigan in 1983 and 1984.
2. Gregarines were found in 31–51% of G.veletis individuals and 50–70% of G.pennsylvanicus.
3. Males were more heavily infected than females in G. veleris , but G.pennsylvanicus males and females had nearly equal infection levels; this disparity resulted in an overall lower infection rate for G. veletis.
4. Both species had fewer gregarines in 1983 than in 1984, possibly due to the adverse effect of drier conditions in 1983 on development of parasite cysts in the soil.
5. Levels of infection were not constant throughout the breeding season for either cricket species.
6. Body size was not correlated with parasite load in either G. veletis or G.pennsylvanicus.
7. Adult age was unrelated to gregarine level in G. veferis , whereas G.pennsylvanicus showed a positive correlation between adult age and parasite load during two non-consecutive weeks of the breeding season.     

DURATION OF STEREOTYPED UNDERWATER VOCAL DISPLAYS BY MALE ATLANTIC WALRUSES IN RELATION TO AEROBIC DIVE LIMIT

During the breeding season from January to mid-April, adult male Atlantic walruses (Odobenus rosmarus rosmarus) dive repeatedly for an average duration of 4–6 min and give stereotyped underwater vocal displays. Between dives, they surface for 1–2 min, take 4–6 breaths, and give stereotyped vocalizations between breaths. Male walruses vocalize in the presence of groups of females and calves, young adult males, or by themselves as lone singers. This pattern is repeated throughout the breeding season and can be maintained for extended periods, sometimes exceeding 48 h. The prolonged underwater vocal displays of male walruses seem possible because the animals do not exceed the aerobic dive limit (ADL), estimated to be 9.8 min for a 1,100-kg animal, nor do they exceed the behavioral ADL of 7.9 min, determined from the histogram of dives for males singing alone. The number of breaths taken after dives and the postdive surface times remained fairly constant despite dive duration, suggesting that the walruses remained within their aerobic dive limits. The duration of most dives made by displaying males vocalizing alone during the breeding season, and dive duration of walruses feeding for protracted periods outside the breeding season, are both roughly half the estimated ADL.     

Male-female interactions of sika deer (cervus nippon) in nara park through allogrooming during breeding and rutting seasons

The frequency and pattern of interactions between males and females of sika deerCervus nippon were surveyed in 3 sites of Nara Park, central Japan, mainly via observation of allogrooming frequency and aggressive behavior throughout the breeding and rutting seasons. In the breeding season, the Daibutsuden group contained several adult males while Ukimido and Hakuba groups contained only a few. Most allogroomers were adult and subadult females. Females groomed the same sex more than the opposite sex at Daibutsuden, but at the other 2 sites, there was no such difference. In general, male-female interactions through allogrooming frequencies in the breeding season were not significantly fewer than intra-sex interactions. Males that attacked females tended to be groomed by females in the breeding season. In the rutting season, all adult males identified in the breeding season were absent at the usual observation sites, and newly arrived males showed defensive and/or mating behaviors. Females groomed adult males in the rutting season regardless of group status or display of sexual interactions. This suggests that male-female allogrooming in the breeding season does not relate to mating in the following rutting season, but may reduce tension in the group during the current breeding season.     

Biology of the annular seabream, Diplodus annularis (Sparidae), in coastal waters of the Canary Islands

The biology of the Canary Islands annular seabream Diplodus annularis (Linnaeus 1758) was studied from samples collected between January and December 1998. Fish ranged from 82 to 209 mm total length in size and from 8.7 to 137.1 g in weight. The mean length showed an increase with increasing water depth. Males showed a negative allometric growth and females isometric growth. The species was characterized by protandric hermaphroditism. The overall sex ratio was unbalanced in favour of males (1 : 0.79). The reproductive season extended from January to May, with a peak in spawning activity in March–April. Males reached maturity at a smaller length (103 mm, 1-year-old) than females (128 mm, 2-year-old). Fish aged 0–6 years were found. The von Bertalanffy growth parameters for all individuals were: L_∞=247.9 mm, k=0.268 years^–1, and t₀=–0.879 years.     

Breeding ecology of the Aquatic Warbler Acrocephalus paludicola on the Biebrza marshes, northeast Poland

Aquatic Warblers Acrocephalus paludicola were studied in a natural fen mire in the Biebrza River valley, the main breeding ground of the species in its entire distribution range. The number of males present and singing at the sample plot changed considerably during the breeding season. Individual identified colour-ringed males sang with unchanged intensity throughout the breeding season. The period of daily singing activity differed from other species of Acrocephalus ; males sang at dusk rather than at dawn. Males took no part in rearing nestlings but remained on territory and showed vigilance behaviour. The density of males in the breeding season ranged from 1.0 to 10.9 per 10 ha. The density of nesting females ranged from 1.3 to 15.7 per 10 ha. In the most suitable habitat females were more numerous than males. The distribution of females (nests) was clumped where potential food resources were higher. Nests were well hidden in places with deeper water between sedge tufts and an abundance of old dry sedge. Females feeding nestlings collected most food within a 5–60-m radius (mean 31.7 m). The return rate of males was higher than that of females. The results suggest a mating system that is intermediate between facultative polygyny and promiscuity.     

Seasonal and diurnal variation in vocal behaviour of the South Island robin

Abstract

The proportion of time spent by South Island robins (Petroica australis australis) of different sex, age, and status giving full song, subsong, and downscales, on a monthly and diurnal basis, is described. Females never gave full song. Males did so throughout the year, but least while moulting. Since bachelors sang significantly more than paired males, song probably functioned largely to attract females. Breeding males sang most during the pre-laying stage. From January to April adult males sang significantly more than immature males, but from May to July the reverse was true. Robins sang mainly in the early morning. Robins generally spent less than 0.5% of time during any stage of the breeding cycle giving sub-song. Outside the breeding season, males spent significantly more time giving sub-song than females, and adult males sang more than immature males. Robins in all categories gave more sub-song during the moult than afterwards. The diurnal pattern of sub-song production was bimodal. About half the downscales were followed by no obvious action from the caller or response from other robins, nor were the calls preceded by an obvious event. About 25% of the downscales were associated with interactions between members of a pair; the remainder were associated with territorial defence. Downscales probably served to maintain contact between members of a pair and to advertise possession of territory. These calls were heard rarely in the breeding season, and most frequently in April. Males gave downscales more than females, but use of downscales by both sexes was evenly distributed through the day.     

THE WINTERING AND MOULT OF RUFFS PHILOMACHUS PUGNAX IN THE KENYAN RIFT VALLEY

Some 5700 Ruffs were ringed in the southern Kenyan rift valley during 1967–79, mainly at Lakes Nakuru and Magadi. These have produced 15 recoveries outside East Africa, 14 in Siberia between 73° and 154°E and one in India. Adult males returned to Kenya mainly during August, and females during late August and early September. Females greatly outnumbered males at all times. Most wintering males departed late in March and early in April, but females not until about a month later. First-year birds appeared from the end of August, but remained in low numbers until late October or November. Most departed during April and May, but a few females oversummered. First-year birds typically accounted for about 25% of the wintering Nakuru females, but about 50% of those at Magadi. At both sites they accounted for a higher proportion of male birds than females. Most of the birds at Nakuru throughout late August to May appeared to be local winterers, and many individuals remained in the area for many months each year. Retrapping indicated that approximately 60% of each season's birds returned the following season. Adult males and most adult females commenced pre-winter wing moult before arrival, but completed most of it in Kenya. Males moulted 3–4 weeks ahead of females, and most had finished before December. Females typically finished during December and early January. Most second year birds timed their pre-winter moult similarly to older adults. Suspension was recorded in over 15% of all moulting birds examined. Adult pre-summer moult involved most or all of the tertials, some or all of the tail feathers, most of the inner wing coverts and the body and head plumage. It occurred mainly during January to March (males) or February to April (females), although tertial renewal commonly began a month earlier. Males showed no sign in Kenya of the supplementary prenuptial moult. First-year birds moulted from juvenile into first winter body plumage during late September to November. They underwent a pre-summer moult similar in extent and timing to that of adults, and again about a month earlier in males than females. Spring feathers acquired were often as brightly coloured as those of adults. About 15% of first-year birds renewed their outer 2–4 pairs of large primaries during January to April. Adult and first-year birds fattened before spring departure, commonly reaching weights 30–60% above winter mean. Weights of adult males peaked early in April, those of adult females early in May, and those of first-winter females later in May. Weights were relatively high also during August and September. This was due to the arrival of wintering birds carrying ‘spare’ reserves, and also apparently to the presence of a late moulting fattening passage contingent. The wing length of newly moulted adults was about 3 mm longer than that of newly arrived first-year birds, but there was no evidence of an increase in the wing kngth of adults with successive moults. Adult wing length decreased by 4–5 mm between the completion of one moult and the middle stages of the next. The migrations and annual timetable of Kenyan wintering Ruffs are discussed, and their moult strategy is compared with that of other Holarctic waders.     

Pup growth of the New Zealand fur seal Arctocephalus forsteri on the Open Bay Islands, New Zealand

Growth of New Zealand fur seal pups was investigated at Taumaka, Open Bay Islands, New Zealand, from November 1974 to September 1976. Pups were weighed and curvilinear length, axillary girth and foreflipper length measured at about ages 55, 190, 235 and 290 days. Males are significantly heavier and larger than females at each age, wtih the exception of axillary girth at 235 days. Pups born during the austral summer of 1974–5 were smaller overall than were pups born during the following summer. This difference was so great that males aged 140 days in 1976 were larger and heavier than males aged 235 days in 1975. Circumstantial evidence suggests that the difference in growth rates of pups born during the two years may have been a consequence, either directly or indirectly, of environmental temperatures. Pups born during the warmer season (1974–5) had the slower growth.     

Age, growth, reproduction and mortality of the striped seabream, Lithognathus mormyrus (Pisces, Sparidae), off the Canary Islands (Central-east Atlantic)

Striped seabream, Lithognathus mormyrus L. (n=731) caught off the Canary Islands from January 1999 to June 2000 were studied. Fish ranged in size from 113 to 372 mm total length, weighing from 21.1 to 748.2 g total weight. Weight increased allometrically with size (b=2.9071). Fish age was 0–10-years-old. Growth was relatively slow (k=0.88 years⁻¹), with females growing at a slightly faster rate than males. The species displayed protandric hermaphroditism. Male : female ratio was unbalanced in favour of males (1 : 0.85). Males predominated in smaller sizes, females in larger sizes, and intersexual individuals were in intermediate sizes. The reproductive season extended from June to December, with a peak in spawning activity in August–September. Males reached maturity at 207 mm (2 years) and females at 246 mm (3 years). The real value of instantaneous rate of natural mortality was between 0.30 and 0.45 years⁻¹.     

Seasonal reproduction in Mexican cottontail rabbits<Emphasis Type="Italic">Sylvilagus cunicularius</Emphasis> in La Malinche National Park,central Mexico

Mexico has the largest number of leporid species in the world but most have been little studied. The endemic Mexican cottontailSylvilagus cunicularius (Waterhouse, 1848) is the largest Mexican rabbit, and although not in danger of extinction, it is increasingly threatened. Since little is known about its annual pattern of reproduction, we studied this species in La Malinche National Park, central Mexico, whereS. cunicularius is still common. For 7 years we trapped and marked 157 different individuals (plus 59, sometimes multiple, re-captures), determining across the year the percent of adult females that were reproductively active, the number of juveniles as a percent of total captures, and the percent of males with scrotal testes. Reproductively active females were present throughout the year but with a notable peak from March to October, juveniles were present throughout the year but with a peak from September to December, and adult males had scrotal testes throughout the year with no seasonal change in testis length. Onset of the breeding season coincided with increasing day length and temperature, and births with high rainfall. Thus, in central MexicoS. cunicularius breeds throughout the year but particularly during the warmer, wetter summer months. We therefore recommend that hunting only be permitted from November to February.     

Spatial and temporal distribution of Antarctic fur seals (Arctocephalus gazella) on the breeding grounds at Bird Island,South Georgia

Summary The number of Antarctic fur seals (Arctocephalus gazella) in the area of the Scotia Sea has been increasing. Observation of their distribution on the breeding grounds are important to help design and interpret censuses. These seals are highly polygynous. In the study area at Bird Island, South Georgia, females give birth and are mated in densely packed colonies located along the shore close to the tideline. Males establish territories in this area, but are also found further inland. This study examined the density-dependent processes regulating the instantaneous size of the male breeding population; the distribution of males in relation to space and the number of females available to be mated and the effect of gregarious behaviour of females on male dispersion. Males were only territorial on the beaches in the areas where most females gave birth and subsequently had their post-partum oestrus. There was an apparent lower (19–20 m²) and upper (40 m²) limit to territory size. Males were excluded from the beach areas when the average density on the beaches was greater than 5 males per 200 m². An asymptotic density of 10–11 males per 200 m² was reached on the beaches and 4–5 males per 200 m² elsewhere. These two asymptotic densities may represent the upper and lower limits of density for a territorial system of dispersion. A model of the temporal changes in female numbers suggested that the total number of females occupying an area of beach during the mating period was approximately twice the number at the peak of the season. There was no indication that males compensated for low female density by increasing territory size. Females and pups became more dispersed after the end of the mating period. It is suggested that one function of gregariousness in females is as a mechanism for mate selection. This study also has implications for methods used to measure population size.     

Cuckoo Hosts in Southern Africa

There is currently no reliable, affordable method of sexing Mauritius Fodies in their first non-breeding season. Ringed immature fodies from a released population on an offshore island were caught in April and May 2005 and sexed in later breeding seasons. Males had longer wing lengths and tarsi than females, with no overlap in wing length between sexes. Males in their first breeding season could usually be differentiated from older males by the paleness and completeness of their breeding plumage. Two adult females grew red feathers characteristic of breeding males in the winter of 2006. It is possible to sex Mauritius Fodies using wing length and separate immature males from adults using the darkness of the bill in the non-breeding season. It is not possible to separate unringed adult and immature females following the postjuvenile and postbreeding moults using current knowledge.     

POPULATION SIZE AND BREEDING SEASON OF THE ANTARCTIC FUR SEAL ARCTOCEPHALUS GAZELLA AT HEARD ISLAND—1987/88

Breeding colonies of the antarctic fur seal Arctocephalus gazella on Heard Island (53°10'S, 73°30'E) are situated on the sheltered northern and eastern coasts on flat vegetated terrain near streams and pools. Pupping in the 1987/88 summer began on 21 November, with 90% of births in 26 d. The median birth date was 11 December. Pup counts at Heard Island made in seven breeding seasons from 1962/63 to 1987/88 show an exponential rate of increase of 21%, which may be inflated due to undercounting in early years. The total of 248 births in 1987/88 represents an exponential increase of 37% since the previous year, but pups may have been undercounted then. Based on the number of pups born, the breeding population is estimated at 870–1,120. During the breeding season, the largest number of animals ashore was 835. Many non-breeding fur seals began hauling out from early January and 15,000 animals were estimated to be ashore by late February, a fat larger number than expected from the size of the breeding population. Both the breeding and non-breeding components of the population may be augmented by immigration. The source of immigrants may be undiscovered breeding colonies of this species in the northwestern sector of the Kerguelen Archipelago or the concentration at South Georgia. Further censuses are required at Heard Island to monitor the population growth.     

Year-round local movements of the japanese fluvial sculpin,Cottus pollux (large egg type), with special reference to the distribution of spawning nests

Year-round local movements of adult Japanese fluvial sculpin.Cottus pollux (large egg type), were investigated by a capture-mark-and-recapture method from July 1989 to July 1990 in the upper reaches of the Inabe River, central Japan. In the pre-breeding (July to January) and post-breeding seasons (June to July), the mean distance of movements in males and females was less than 20 m, and there was no apparent tendency to move into a particular channel-unit habitat, suggesting residential tendency in both sexes. In the breeding season (February to May), males tended to move into the raceways where most of the spawning nests were found, but females did not do likewise, indicating a sexual difference in movements in that season. Such sexual difference in movements was also confirmed by the records of individuals captured and recaptured more than three times: six (42.9%) of 14 males moved into the raceways in the breeding season, whereas only one (7.1%) of 14 females did so in that season. The reason behind this sexual difference in movements observed in the breeding season is discussed from the viewpoint of the patterns of spatial distribution between sexes during the pre-breeding and breeding seasons.     

Sexual competition in an inbreeding social spider,Stegodyphus dumicola (Araneae: Eresidae)

Summary Sexual competition is shown to occur in the social spiderStegodyphus dumicola (Eresidae). While the secondary sex ratio inS. dumicola was female-biased, the overall operational sex ratio (numbers of breeding males to breeding females over the season) showed no strong female bias. Males matured before females and had a shorter lifespan than the females. Mating took place in the natal colony. Males fought over access to the few mature females available early in the reproductive season, but females appeared to control the duration of mating. Later in the season, some adults of both sexes dispersed alone to breed elsewhere. We conclude that different rates of maturation between the sexes within a colony provide the opportunity for females that mature early in the season to be choosy in selecting a mate and this forces males to compete. Early reproduction may be beneficial for both females and males, because the offspring of females that reproduce early may have a competitive advantage over later (and smaller) offspring in the colony.     

The biology of the stoat (Mustela erminea) in the National Parks of New Zealand IV. Reproduction

Abstract

The gonads of 528 female and 821 male stoats were examined. The weights of ovaries and testes in adults peaked simultaneously in October, the season of births and of post-partum oestrus. Of 73 females, 78% had even numbers of nipples, mostly 8 or 10. The mean number of embryos in 13 pregnancies was 8.8 (6–13), and embryo weights ranged from 0.005 g to 2.9 g. Of 11 pregnant females, 8 contained fewer embryos than corpora lutea, and there was evidence of transuterine migration of blastocysts in 6. All but 2 of 451 females caught in December–July inclusive carried corpora lutea of delay. Few adult and no young females were found in oestrus in September–October, though adult males were fertile from August to February (no first-year males were fertile). There was some evidence that the breeding season started later at more southerly latitudes in both males and females. The mean number of corpora lutea per female was 9.7 (n = 439), and there was a significant inverse correlation between counts for the 2 ovaries of one individual. There was generally no significant variation in fecundity of females with age, body weight, or year. Of 11 females which were considered to have lost their litters, 10 were collected in beech (Nothofagus) forests. Four females and 9 males had abnormal gonads; the most severe abnormality was an ovarian teratoma of unknown pathology.     

The reproductive biology, age and growth of the North American cyprinid, Notropis longirostris (Hay)

Notropis longirostris (Hay), the longnose shiner, in Catahoula Creek, Jourdan River drainage, Hancock County, Mississippi, was studied from May 1970 to May 1972. In 1971 reproduction occurred from late March into October, as indicated by gross examination of testes, breeding tubercles and breeding colour in males, and ovarian weights, measurements of ova, and gross examination of ovaries in females. Gross examination of ovaries in 1970 also indicated an extended reproductive season. Generally no significant differences from a 1 : 1 sex ratio or in the size of males and females in collections taken during the reproductive season were indicated. Males and females matured about the same size. Most females were sexually mature when 29–30 mm SL. The smallest female with mature ova was 28 mm; however, the majority of females did not have mature ova until 31–33 mm. The number of mature ova produced prior to spawning ranged from 15 to 129 for females 30.8–44 mm SL. There were significant differences in the number of mature ova with time, two peaks being indicated: the first in late March and April at the beginning of the reproductive period and the second in early July about the middle of the season. This conclusion is also supported by ovarian weight measurements and length frequency histograms. The mean diameters of mature ova ranged from 0.70–1.05 mm, averaging 0.90 mm, and were not significantly correlated with length. Most fish live about 1–1.5 years and do not live through two winters, indicating an annual turnover in the population. Maximum size was about 48 mm SL. Specific characteristics of the life history pattern of N. longirostris are discussed in relation to ecological conditions of the habitat.