Female reproductive strategies in bar-headed geese (Anser indicus): Why are geese monogamous?

Summary In a semi-captive flock of Anser indicus with a surplus of females, permanent harem groups consisting of one male with one to five females, lasting for up to several years, were regularly observed. Polygynous groups contain one paired female to which the male is most attentive and secondary females which follow the paired male and are tolerated by the pair. Average annual reproductive success was lowest in lone females (0.02 young fledged per year), higher in secondary females (0.23 young) and highest in paired females (0.56 young per year). Differences seemed due to different degrees of male assistance. Secondary females could not be shown to be competitors of paired females in annual reproductive success. Lone females became secondary females mainly after an age of 3 years, i.e. when their chances to pair had dropped significantly. Females were more likely to become secondary instead of paired females in years when the adult sex ratio was more heavily female biased. As sex ratios in wild geese are usually around 1:1 or even biased towards males, females will not usually need to resort to the suboptimal secondary-female strategy. Hence, geese usually live in monogamous pairs instead of harem groups.     

Dispersal, pair formation and social structure in gibbons (Hylobates lar)

We report observations on reproduction, natal dispersal, pair formation, and group structure based on longitudinal observations of several white-handed gibbon (Hylobates lar) groups spanning 18 years. Our observations are at odds with the traditional view that gibbons live in nuclear family groups consisting of a pair of adults and their offspring, and that parents exclude young from the family territory when they reach adult size. In the relatively dense Khao Yai study population, dispersing young usually obtain mates by replacing adults in existing territories, which creates non-nuclear families. Six subadults, five males and one female, matured and dispersed at an average age of 10 years, or about 2 years after reaching adult size. Average natal dispersal distance was 710 m, or between one and two territories away. At least two dispersing males replaced adults in neighboring groups. In one case, forcible displacement of the resident male resulted in a group which included a young juvenile presumably fathered by the previous male, two younger juveniles (probably brothers) from the new male's original group, and (later) offspring of the new pair. Social relations within this heterogeneous group remained harmonious: the adults groomed all the young and play occurred between all preadult members. In only two out of a total of seven cases of dispersal seen did two subadults pair and disperse into new territorial space. Nonreproducing subadults which delay dispersal may be tolerated by the adults provided that they contribute benefits to the adults or their offspring. Possible benefits include behaviors such as grooming, social play with juveniles, and support of the adult male in defending the territory. Delayed dispersal is probably advantageous in a saturated environment where there is no room for floaters, but subadults may also gain indirect fitness benefits by aiding siblings and other relatives. Received: 24 January 1997 / Accepted after revision: 12 January 1998     

Social organization of woodchucks (Marmota monax)

Summary The social organization of woodchucks (Marmota monax) in southeast Ohio was studied at two sites, at one for two 2 years (1979–1980) and the other for 3 years (1981–1983). Spatial organization was determined by trapping and radio tracking. The home ranges of adult females did not overlap in the early spring but during late spring and summer there was some overlap (<10%) as females expanded their home ranges. Adult females tended to occupy the same home range in consecutive years. Some adult males occupied well-defined home ranges that did not overlap the home ranges of other males but did overlap extensively the home range of one to three adult females. These males tended to occupy the same home range in consecutive years. Infants used the same home range of their dam until about 2–3 months of age when most males and females apparently dispersed. About 35% of the juvenile females did not disperse until their second spring, just before their mother's new litter first emerged from their burrow. The average social group consisted of an adult male with two female kin groups comprising an adult female, an offspring (usually female) of the previous year, and the young of the year. Interactions within the kin group and with the adult male were relatively frequent and generally amicable. Interactions between kin groups both within and between different social groups were relatively rare and agonistic. The social organization of woodchucks in Ohio differs from that described in previous studies of woodchucks elsewhere and from that predicted by current models proposed by others on the evolution of social organization of marmots.     

Effect of pair-bonding with adults on the ontogenetic manifestation of aggressive behavior in a primate,Saguinus fuscicollis

Summary Injurious aggression, scent marking and some visual displays shown in situations analogous to territorial defense were studied in young saddleback tamarins who had lived with nonrelated adult and juvenile social partners from 6 months of age under the experimental conditions outlined below. Twenty male and 20 female tamarins were removed from their natal families when 6 months old, and were used to form pairs and trios of the following composition: (1) one juvenile female and one juvenile male (10 pairs); (2) one juvenile female and one adult male (4 pairs); (3) one juvenile female, one juvenile male, and one adult male (6 trios); (4) one adult female and one juvenile male (4 pairs). These groups cohabited permanently and when the subjects were between 10 and 12 months old, their social interactions with adult conspecific strangers were studied, using series of 10-min social encounter tests. During these tests injurious aggression (attacks, fights, chases), a number of visual hostile displays (threat face, ruffle, arch) and scent marking were recorded.Young males and females living with adults of the opposite sex showed more injurious aggression against strangers and scent marked more frequently than young subjects living with partners of their own age. Males living with adult females also showed more facial threat than males living with young females (Figs. 1 and 2). Young males living in trios with adult males and young females scent marked less frequently than males living only with a young female. Aggression, scent marking and facial threat shown by subjects living with adult sex partners were at the level of socially and sexually experienced, pair-bonded adults (Fig. 3). No differences in ruffling and arching scores were found. The injurious aggression scores of the subjects were correlated with those of their mates. These results show that tamarins can fulfill the behavioral roles of pair bonded adults and also breed (Epple and Katz 1980) at an unexpectedly early age, when they live under the influence of an adult sex partner. Young animals cohabiting with an adult of the same sex, on the other hand, show a trend toward inhibition of adult-like behaviors.     

On the mating system of the cooperatively breeding saddle-backed tamarin (Saguinus fuscicollis)

Summary This paper reports on 5 years of observatiors of individually marked saddle-backed tamarins (Saguinus fuscicollis, Callitrichidae). Although callitrichids have long been presumed to have a monogamous social system, this study shows that the breeding structure of saddle-back tamarin groups is highly variable. Groups most commonly include two or more adult males and a single reproductive female, but occasionally contain only a single pair of adults, or less often, two reproductively active females and one or more males. Data on group compositions, group formations, intergroup movements and copulations show that the social and mating systems of this species are more flexible than those of any other non-human primate yet studied. Infants (usually twins) were cared for by all group members. There were two classes of helpers: young, nonreproductive individuals who helped to care for full or half siblings, and cooperatively polyandrous males who cared for infants whom they may have fathered. The observations suggest that non-reproductive helpers may benefit from their helping behavior through a combination of inclusive fitness gains, reciprocal altruism, and the value of gaining experience at parental care.     

Population dynamics of the commensal spider crab Inachus phalangium (Decapoda: Maiidae)

The ecology of the spider crab Inachus phalangium (Fabricius, 1775) (Decapoda: Maiidae) was studied in the field. I. phalangium inhabits the sublittoral on the sea anemone Anemonia sulcata Pennant. From July 1981 to April 1984 in the Mediterranean (Banyuls sur Mer, southern France) more than 3000 anemones were examined and ca 1800 I. phalangium were found on them. The population dynamics' generation cycles, reproductive activities and the dynamics of the sex ratio were investigated. The density of juveniles (crabs before the pubertal moult) on anemones changed in a yearly cycle from low in the first six months to very high in the second six months. The first occasional young crabs of a generation appeared in March/April (3rd and 4th decapodite stages) on the anemones. Their density increased enormously in the following months. The generation grew gradually on the anemones and moulted into puberty in September-January. Density of adults (crabs after the pubertal moult) on anemones changed in a yearly cycle from low to high from the summer to winter months. A new adult generation was recruited every autumn through the pubertal moult and disappeared in the following summer. Female reproductive activity continued throughout the year. Females carried several broods in succession, but the frequency of breeding females fluctuated on a yearly cycle. The highest percentage of egg-carrying females, i.e. the peak of the reproductive season, lay in the first half of the year. The maximal life span of a generation, from the hatching of the first larvae to the disappearance of the last adults, lasted 1.5 to 2 years. Males moulted into puberty ca one month later than females. The moulting distribution of adult males had roughly the same course as in females. An adult male generation diet out about one to two months before the female generation. Life expectancy was therefore 14 to 17 months for females and 12 to 15 months for males. The sex ratio of juveniles shortly before the pubertal moult was balanced. The sex ratio of adults shifted from 1:1 at the beginning of the reproductive period to ca 1:9 in favour of females at its end.     

Paternal age and offspring growth: separating the intrinsic quality of young from rearing effects

Younger individuals are often less successful in reproduction than older ones. This might be because of improving breeding skills with age or because the genetic quality of young or early maternal effects on them vary with parental age. However, no attempt has been made to experimentally separate these processes in vertebrates. We conducted a cross-fostering experiment in collared flycatchers (Ficedula albicollis) in three breeding seasons to disentangle origin- and rearing-related effects of paternal age on chick growth, while controlling for date-specific environmental conditions as well as differences in clutch and brood size. The age of the male at the nest of origin, but not that of the rearing male, had a year-dependent effect on nestling body mass and tarsus length. In two seasons, young of subadult males grew slower in the early linear phase of growth than young of adult males. There was no compensatory growth in the final asymptotic phase, so both body mass and tarsus length before fledging reflected the differential early development. In the remaining year, the age of the male at the nest of origin had no significant effect on chick growth. The environment-dependent origin effect we detected was unexplained by incubation times, hatching asynchrony, chick masses at swapping or previously described age-dependent egg quality patterns. Our results therefore suggest a genotype × environment interaction on the relative development of offspring sired by subadult and adult males. Our results also raise the possibility that female birds may gain genetic benefits by mating with older males. Further studies should identify general patterns of male age-dependent female mate choice and offspring quality in different environmental conditions.     

Sexual dimorphisms in radula of<Emphasis Type="Italic"> Conomurex persicus</Emphasis> (Gastropoda: Strombidae) in the Mediterranean Sea

Dentition characters of Conomurex persicus found along the Mediterranean coasts of Turkey were analyzed. For the analyses of radula, 289 individuals (34 adult males, 140 adult females and the remainder juveniles) were examined. Male and female individuals of the species had different numbers of radular cusps. The radula of the taenioglossate type was made up of two marginal teeth, one lateral and one central (rhachidian) tooth, each being delicate and with different numbers of cusps. The central and lateral teeth had seven cusps and five cusps, respectively, in both males and females. Outer and inner marginal teeth of males had two and one cusps, while those of females had five and six cusps, respectively. The females radula is yellow-whitish. The males radula is reddish dark brown.Communicated by O. Kinne, Oldendorf/Luhe     

Association networks in spider monkeys (<Emphasis Type="Italic">Ateles geoffroyi</Emphasis>)

We use two novel techniques to analyze association patterns in a group of wild spider monkeys (Ateles geoffroyi) studied continuously for 8 years. Permutation tests identified association rates higher or lower than chance expectation, indicating active processes of companionship and avoidance as opposed to passive aggregation. Network graphs represented individual adults as nodes and their association rates as weighted edges. Strength and eigenvector centrality (a measure of how strongly linked an individual is to other strongly linked individuals) were used to quantify the particular role of individuals in determining the network's structure. Female–female dyads showed higher association rates than any other type of dyad, but permutation tests revealed that these associations cannot be distinguished from random aggregation. Females formed tightly linked clusters that were stable over time, with the exception of immigrant females who showed little association with any adult in the group. Eigenvector centrality was higher for females than for males. Adult males were associated mostly among them, and although their strength of association with others was lower than that of females, their association rates revealed a process of active companionship. Female–male bonds were weaker than those between same-sex pairs, with the exception of those involving young male adults, who by virtue of their strong connections both with female and male adults, appear as temporary brokers between the female and male clusters of the network. This analytical framework can serve to develop a more complete explanation of social structure in species with high levels of fission–fusion dynamics. This contribution is part of the special issue “Social Networks: new perspectives” (Guest Editors: J. Krause, D. Lusseau and R. James)     

Snake-directed mobbing by the Formosan squirrel Callosciurus erythraeus thaiwanensis

Summary The Formosan squirrel Callosciurus erythraeus thaiwanensis was often observed mobbing the snake Elaphe climacophora. A total of 36 natural and 21 experimentally induced mobbings were observed and analyzed. The number of attending squirrels per mobbing event varied from one to seven, and 84% of observed mobbings were performed by more than one individual. The duration of a mobbing bout increased directly with the number of assembled mobbers. In 68% of cases, one adult female was one of the mobbers; there was never more than one female per mob. The number of assembled males per mob varied from 0 to 5; 40% of the mobbings involved two or more males. This difference is correlated to a difference in spacing patterns of both sexes; female home ranges were distributed exclusively, whereas male home ranges overlapped each other. Females mated with multiple males whose home ranges overlapped theirs. Female's reproductive status (conception, lactation, and weaning) affected their intensity of response to the playback of mobbing calls, females in pup-rearing period being the most sensitive. One function of the mobbing appears to be defense of the young against snake predation. Females mobbed more intensively and longer than males. Males that had resided at the study site for at least 1 year tended to mob more frequently than intruders.     

Spatial organization and mating system of Microtus townsendii

Summary Space use by individual Townsend's voles, Microtus townsendii, was investigated in spring and summer by means of radiotelemetry and intensive live trapping in undisturbed grasslands near Vancouver, British Columbia. Home ranges of males were larger than those of females; females had significantly larger ranges in spring than in summer. Most males and females maintained territories free of individuals of the same sex in spring. Male-female pairs had their exclusive territories closely overlapping each other. The 1:1 operational sex ratio and the spatial association of pairs of males and females suggest that the voles were monogamous in the spring of 1988 and that 50% of the males were monogamous in the spring of 1989. In summer, there was more intrasexual overlap between home ranges of males and females and female ranges were considerably smaller than those of males. Females were more philopatric than males and females thought to be members of the same family group lived adjacent to each other or had overlapping home ranges. Males overlapped with more than one female in summer, but most females still overlapped with only one male, which suggests that the mating system is polygynous in summer. Thirty-five percent of the philopatric females became pregnant for the first time when the male spatially associated with their mother in the spring was still alive and thus could potentially have mated with their fathers. Male and female territoriality in spring is the proximate mechanism for the limitation of breeding density by spacing behaviour.[/p] Offprint requests to: C.J. Krebs     

Mud crab predation on ribbed mussels in salt marshes

Mud crab (Panopeus herbstii H. Milne Edwards) predation on Atlantic ribbed mussels (Geukensia demissa Dillwyn) was studied by a series of laboratory and field experiments at two sites at Morehead City, North Carolina, USA from 1987 to 1989. Tidal elevation had no effect on predation intensity, although mud crabs were active only when they were submerged. Horizontal distance from the water-marsh edge significantly affected mussel mortality in one of two winter experiments, despite the occurrence of virtually all the crabs at the marsh edge. Of the juvenile mussels attached to adult mussels, those totally buried in the sediment suffered mortality from mud crab predation at a rate not detectably different from those exposed above the surface. Juveniles attached to adult conspecifics, however, experienced significantly less mortality than those attached to oysters. Interestingly, the two groups of mussels (those attached to conspecifics and those attached to oysters) display shell morphological dimorphism. The more oblate shells of the mussels attached to oysters as compared to those attached to conspecifics might be induced by the higher predation rate. Alternatively, slimmer shells from individuals attached to conspecifics may be the result of living within physically compact mussel clumps.Please address all correspondence and requests for reprints to Dr Lin at his present address: Smithsonian Environmental Research Center, P.O. Box 28, Edgewater, Maryland 21037, USA     

The population biology of the living coelacanth studied over 21 years

Between 1986 and 2009 nine submersible and remote-operated vehicle expeditions were carried out to study the population biology of the coelacanth Latimeria chalumnae in the Comoro Islands, located in the western Indian Ocean. Latimeria live in large overlapping home ranges that can be occupied for as long as 21 years. Most individuals are confined to relatively small home ranges, resting in the same caves during the day. One hundred and forty five coelacanths are individually known, and we estimate the total population size of Grande Comore as approximately 300–400 adult individuals. The local population inhabiting a census area along an 8-km section of coastline remained stable for at least 18 years. Using LASER-assisted observations, we recorded length frequencies between 100 and 200 cm total length and did not encounter smaller-bodied individuals (<100 cm total length). It appears that coelacanth recruitment in the observation areas occur mainly by immigrating adults. We estimate that the mean numbers of deaths and newcomers are 3–4 individuals per year, suggesting that longevity may exceed 100 years. The domestic fishery represents a threat to the long-term survival of coelacanths in the study area. Recent changes in the local fishery include a decrease in the abundance of the un-motorized canoes associated with exploitation of coelacanths and an increase in motorized canoes. Exploitation rates have fallen in recent years, and by 2000, had fallen to lowest ever reported. Finally, future fishery developments are discussed.     

Social relationships in a cooperatively polyandrous group of tamarins (Saguinus fuscicollis)

Summary This paper presents detailed data on the social relationships among the adults, and between the adults and young, of a cooperatively polyandrous saddle-back tamarin (Saguinus fusciollis; Callitrichidae) group studied for one year. Some data are also presented from groups studied in other years. Adult males in the study groups gave more grooming than they received, while the opposite was true for females (e.g. Fig. 1). The two polyandrous males in the main study group were very rarely aggressive to each other, rarely tried to disrupt each others' copulations, groomed each other, and occasionally shared food, suggesting that their relationship was more affiliative than agonistic. Data on grooming (Fig. 2), spatial relationships, and the initiation of copulations suggest that the males of this group, may have been somewhat more responsible than the female for the maintenance of male-female relationships. Both males and females performed all forms of parental care except lactation. In the main study group each of the males groomed the offspring and remained in close proximity to them more than did the female (Figs.3 and 4). These data are compared with existing data on social relationships in bird species that exhibit cooperative polyandry.     

Bigamy and mate choice in the biparental cichlid fish Cichlasoma nigrofasciatum

Summary Sixty percent of C. nigrofasciatum males showed bigamous behaviour when held in small, outdoor ponds at an adult sex ratio of 5 males to 10 females. No male held more than two pair bonds simultaneously. Bigamy had reproductive benefits; bigamous males, on average, fathered more broods that survived well into the free-swimming fry stage than did monogamous males. In ponds where adult size varied, no positive correlations were found, for either sex, between adult size and frequency of spawning or success of broodrearing, despite predictions that larger size would confer reproductive benefits on both sexes. A significant positive correlation was found between the sizes of mated individuals in the pond where both sexes varied in size. On theoretical grounds this relationship is likely to be more strongly influenced by female than by male choice of spawning partner.     

Male age structure influences females’ mass change during rut in a polygynous ungulate: the reindeer (Rangifer tarandus)

The manipulation of the sex ratio and age structure in many managed ungulate populations calls for a better understanding of their potential consequences on females’ condition and behavior during rut. During 1996–2002, we manipulated the male age structure and male percentage (nine treatments during 7 years) within an experimental herd of semidomestic reindeer (Rangifer tarandus) and investigated their influence on both the body mass change and the behavior of females during rut. On average, the females lost body mass (−0.95±SE 0.18 kg) during rut, which we contend to reflect somatic costs. The females’ losses increased as the percentage of male decreased, but this was certainly ascribed to one treatment with high male percentage (27.7%) as compared to the others (ranging from 3.9 to 12.2%). Female losses were highest for treatments including both young and adult males as compared to only adult or only young males, and higher for treatments including only young compared to only adult males. This is supported by (1) the higher female harassment frequency when females are exposed to only young or a mixture of young and adult males as compared to only adults, (2) the higher female harassment frequency by young males as compared to adults in the mixed treatments, and (3) the reduced females’ feeding activity in treatments including both young and adult males. We conclude that the male age structure during rut will influence the females’ behavior and mass change and may have implications for females’ life history and for population dynamics.     

Female choice in the opportunistic mating of wild chimpanzees (Pan troglodytes schweinfurthii) at Mahale

For female chimpanzees (Pan troglodytes schweinfurthii) in the Mahale Mountains National Park, Tanzania, the most common mating pattern is opportunistic. In such opportunistic matings, females copulated promiscuously but not randomly. This study describes female mate choice during 1-year observation of six females who exhibited regular genital-swelling cycles. During the study period, 169 opportunistic matings and four restrictive matings were recorded over the course of 51 days. As female estrus progressed, mating frequency and the number of adult male mating partners increased, although the number of potential mating partners did not change. Criteria of female choice examined were the direction and consent/rejection of courtship, proximity maintenance, and female grooming. Adult-male courtships were successful more often than those of adolescent males. During the earlier phase of estrus, females copulated rather promiscuously with many males. But during the later phase of estrus when the likelihood of conception is expected to be highest, they copulated repeatedly with high-ranking adult males. There was a positive correlation between female grooming frequency and mating frequency when the likelihood of conception was greatest. Female chimpanzees are thought to choose high-ranking males as fathers of their offspring. Moreover, female chimpanzees may adopt one or both of two mating strategies, i.e., a many-male strategy and a best-male strategy. Received: 23 November 1998 / Received in revised form: 12 April 1999 / Accepted: 26 April 1999     

Temporal life history plasticity of the Southern Ocean squid <Emphasis Type="Italic">Todarodes filippovae</Emphasis> from waters off Tasmania,Australia

Population dynamics and maturity parameters were analysed for seasonal samples of the oceanic ommastrephid squid Todarodes filippovae from off the coast of Tasmania Australia from 2002 to 2004. Based on assumed daily periodicity in statolith increments, T. filippovae had a life cycle of about a year with the sexually dimorphic females reaching their larger size by predominantly growing faster than males. Due to the small sample size of males, analysis was undertaken on female individuals only. Growth in all samples was best described by a power curve and varied annually, with significantly faster growth in 2001 compared to the subsequent 2 years. Seasonal growth rates also varied with autumn- and winter-hatched squid significantly faster than summer-hatched squid. Spring growth rates were intermediate but not significantly different to the other three seasons. Peak hatching periods occurred in late autumn and early winter. ANOVA revealed a season × year interaction for mantle length and total body weight. Pairwise comparisons showed that the annual differences were likely driven by smaller squid in autumn 2002 compared to autumn samples in the other 2 years. Pairwise comparisons also revealed seasonal differences with winter-caught squid smaller than those from the majority of other samples. There were no seasonal effects on mature female gonad weights but females caught in 2002 had significantly lighter gonad weights than females from the following 2 years. There were no consistent trends among seasons or years in the age structure of mature females. This study revealed the plasticity and flexibility in growth and maturity parameters in this species, with a preference for faster growth during cooler periods.     

Spatio-temporal distribution and migration of adult male loggerhead sea turtles (Caretta caretta) in the Mediterranean Sea: further evidence of the importance of neritic habitats off North Africa

Ten adult male loggerhead sea turtles, captured by trawlers or dip nets, were satellite-tracked from a neritic foraging ground in the Mediterranean in order to investigate adult spatio-temporal distribution and breeding migration. Five individuals migrated to potential breeding sites in Libya and one to Greece. The results complement previous studies and show that: (1) the Tunisian shelf may be more important for turtles from Libyan rookeries than previously thought; (2) male tracks corroborate a conservation hotspot previously identified for juveniles; (3) the north African coast represents a preferred migratory corridor, unless open sea routes are more direct; (4) adult males may exhibit high fidelity to relatively small areas, without evident seasonal differences; (5) adults home ranges were smaller and more neritic than juveniles frequenting the same area; (6) males may frequent multiple courtship areas; (7) the average remigration interval of males frequenting this region is longer than 1 year.     

Distribution,growth and life cycle of the mesopelagic amphipod Primno abyssalis (Hyperiidea: Phrosinidae) in the southern Japan sea

The vertical distribution, growth, maturation, brood size and life cycle of the hyperiid amphipod Primno abyssalis (formerly P. macropa) were investigated using seasonal samples collected from Toyama Bay, southern Japan Sea, during the period June 1986 to September 1992. Over four different seasons of the year, P. abyssalis was most abundant in the 200 to 350 m strata at night and the 350 to 400 m strata during the day, indicating 100 to 150 m as the general distance of diel vertical movement. Some differences in vertical migrating behavior were noted among juveniles, adult males and females. Population-structure analysis revealed the occurrence of three cohorts aged 0+, 1+ and 2+ yr. Growth as body length in this species is linear with time. Estimated time to complete one life cycle is 1.8 to 2.5 yr for females, but only 0.8 yr for males. Maximum longevity is 2.8 yr. Instar analysis based on the segment number of pleopod rami indicated that newly hatched juveniles molt ten times to reach adult male, and four more times to reach adult female. Adult instar number was found to be only 1 for males and 5 for females. Ovigerous females occurred throughout the year, but the annual peak of release of juveniles from the female's marsupium is estimated to be arly March. Brood size was not correlated with female size, a maximum brood size of 214 eggs was recorded. The dry and ash-free dry weights of instars suggested that juveniles in the female marsupium, adult males, and older adult females are less active feeding or non-feeding stages. Except for the reduced growth rate and the occurrence of small, short-lived males, most characteristics of P. abyssalis are consistent with the present view of the life modes of mesopelagic animals, including linear growth in length, aseasonal reproduction, and smaller brood size coupled with larger eggs.