Immature Males Research Articles

Spatial interrelations between bank voles and yellow-necked mice in Crabapple Island

The investigations on spatial co-occurrence between Myodes (Clethrionomys) glareolus and Apodemus flavicollis conducted on Crabapple Island (NE Poland) in 1994 through 1999 reveal that: single mature females of both species often occur in the same places, whereas local groups of such females rarely cohabit the same place. Mature males of these species always avoid sites occupied by males of the other species. Immature males, however, seem to be mutually indifferent.

Secondary sex ratios do not support maternal manipulation: extensive data from laboratory colonies of spiny mice (Muridae: Acomys)

Spiny mice of the genus Acomys (Muridae) represent a very suitable mammalian model for studying factors influencing the secondary sex ratio (SSR). The maternal effort in these rodents is extremely biased in favour of the prenatal period and, therefore, maternal manipulation of the SSR is potentially more advantageous. We studied the SSR in four populations/species of spiny mice kept in family groups consisting of two closely related females, one non-relative male and their descendants. The groups were established from founding animals aged about 3 months (maturing age) and were allowed to breed freely for several months. Each litter was sexed after birth, and relevant data were thoroughly recorded. Altogether, data were collected on 1684 litters: 189 of Acomys sp. from Iran, 203 of A. cilicicus, 875 of A. cahirinus, and 417 of A. dimidiatus. We recorded the sex of 4048 newborns of which 1995 were males and 2053 were females. The overall sex ratio was close to 1:1 (49.2%). Generalized linear mixed models and/or generalized linear models were constructed to evaluate the effect of four life history and eight social variables on the sex ratio. No consistent effects of these variables on the sex ratio were found and, interestingly, none of the variables associated with maternal life history had any effect on the sex ratio. Three factors associated with group composition (i.e. the number of immature males, the number of immature females and the number of breeding females) did have significant effects on the sex ratio, but these effects were not consistent across the studied species. In conclusion, our evaluation of this large dataset revealed that the sex ratio in spiny mice is surprisingly stable.

Seasonal variation in energy expenditure and body composition in captive White Storks ( Ciconia ciconia)

North Western European populations of White Storks ( Ciconia ciconia) appear to have been saved from extinction by settling, i.e. stopping migration. Settled storks exposed to winter conditions must cope with periods of potentially high energy demands that would otherwise be avoided by the migration process. Doubly labeled water (DLW) was therefore used to examine the seasonal variation (summer vs winter) in daily energy expenditure (DEE) and the body composition of adult and immature storks of both sexes. Male White Storks showed a higher DEE over the winter period than in summer compared with females; in particular, immature males exhibited greater energy expenditure in winter than adult males. Thus, the DEE did not significantly differ between summer and winter (except for immature males), reflecting an absence of thermoregulation cost in winter. For both age classes, total body mass increased in winter, which was mainly due to an increase in fat mass. Adult storks were 5% heavier than immature storks. The sexes differed in body mass, with males weighing significantly more than females by 11%. Mean LBM (lean body mass) was 8.5% higher in adults than in immatures, and was 11.5% higher in males compared with females. Between their first and second summers, immatures accumulated a lean body mass to finally reach the same values as adults, indicating a phase of muscle development. The mean fat mass of the storks did not differ between age classes or between sexes. Based on physiological parameters, this study shows that settled White Storks are able to cope with mild winter periods when they are artificially provided with food. In a view to preserve favourable habitats for this species, it is therefore necessary to decide on a plan of action for breeding areas.

Sex biased intra‐tree oviposition site selection and larval foraging behavior of a specialist herbivore

AbstractHeterogeneity in the quality of oviposition and feeding sites within plants can significantly influence the distribution and abundance of herbivorous insects, but remains poorly understood. Field surveys and a manipulative study were conducted to evaluate the influence of variation within the crown of black spruce, Picea mariana (Mill.) B.S.P. (Pinaceae), on adult oviposition and larval feeding behavior of yellowheaded spruce sawfly, Pikonema alaskensis Rohwer (Hymenoptera: Tenthredinidae). Most eggs were laid in the mid to lower crown of 1.5–2 m tall trees. However, most of the few eggs that were laid in the upper crown (i.e., whorl 2) were female. Fourth and fifth instars dispersed acropetally, from the mid and lower to the upper crown, causing high defoliation in the upper crown. Late‐instar females were generally more abundant than males on the leader, the most apical shoot on a tree where eggs and early instars rarely occurred, strongly suggesting that more females than males disperse acropetally. This hypothesis was supported in a manipulative experiment, where only 15–20% of larvae in all‐male broods, but almost three‐quarters of larvae in mixed broods, dispersed to the upper crown. To our knowledge, this is only the second study to explicitly demonstrate preferential allocation of progeny sex through oviposition site selection by a herbivorous insect, and the first study to unambiguously demonstrate sex‐biased dispersal by the juveniles of an insect whose adult females can fly. This study emphasizes the important role of intra‐plant variation in shaping both oviposition site selection and the dispersal behavior of juvenile phytophagous insects within their hosts, and suggests that sex‐biased foraging behaviors may be necessary for some insects to accommodate the respective needs of immature females and males within heterogeneous host plants.

Molecular Evaluation of the White-tailed Deer (Odocoileus Virginianus) Mating System

We used genetic-based paternity assignments from 3 diverse populations of white-tailed deer (Odocoileus virginianus) to evaluate the long-held assumption that male reproductive success in this species is highly skewed toward a small number of mature, dominant individuals. The study populations represented a range of adult sex ratios and male age structures. Male reproductive success was distributed among a large number of males in all populations, with no evidence for highly skewed access to mating for any individual male. Surprisingly, physically immature males (1.5 and 2.5 years of age) collectively fathered 30–33% of offspring in all populations, even where mature males were present. Ecological and behavioral variables appear to constrain the ability of individual males to monopolize access to females, resulting in a wider distribution of reproductive success than expected based on previous ecological and behavioral studies of white-tailed deer. Qualitative differences in the distribution of male reproductive success among study sites suggested that demographic attributes such as adult sex ratio and male age structure might influence the degree of competition for mates. Further study incorporating known-age cohorts or integrating movements and behavior is necessary for understanding the effects of population demographics as well as the physical and behavioral attributes that confer reproductive success in diverse populations of white-tailed deer.

Age‐dependent pattern of connexin43 expression in testes of European bison (Bison bonasus, L.)

Morphology and the expression of connexin43 (Cx43) was investigated in testes of immature, prepubertal, and adult European bison bulls by means of routine histology, immunohistochemistry, and Western blotting, respectively. Testes were collected from culled animals living in Bialowieza and Borecka Forests, Poland. Histological examination of testicular tissue of immature and prepubertal males revealed normal structure, whereas of adult individuals either normal testicular structure with advanced spermatogenesis or varying degrees of tubule and interstitial tissue abnormality were seen. Immunohistochemical studies revealed Cx43 signal mostly at Leydig cell membrane appositions. In testes of immature males heterogeneous staining was observed; its intensity markedly increased in prepubertal males reaching almost two times more intense staining in adults. Strong Cx43 signal between Leydig cells was also observed in testes with structural alterations; however, sporadically it was of weak linear pattern. In the tubules of the latter, the intensity of Cx43 staining was weak to moderate or it was even absent. Immunohistochemical qualitative analysis was confirmed by quantitative image analysis in which the staining intensity was expressed as relative optical density of diaminobenzidine deposits. Data from Western blot analyses confirmed the results obtained by immunohistochemistry; immunodetectable Cx43 protein as a band of 43 kDa was detected in all testes samples. Overall, the increase in Cx43 level in testes along the bison postnatal development may be capable of a better exchange of metabolites and coordinating Leydig cell activity during maturation. A relationship between homozygosity occurring in European bison and altered intercellular communication is suggested.

Biological and reproductive characteristics of the Patagonian smoothhoundMustelus schmitti(Chondrichthyes, Triakidae) as documented from an artisanal fishery in Uruguay

The use of a highly selective fishing gear is the main reason for mature individual dominance in the Patagonian smoothhound (Mustelus schmitti Springer, 1939) artisanal fishery in Punta del Diablo, Uruguay. Differences in length–weight relationships (LWR) and size at 50% maturity (L50) within its distribution were also expected. A total of 696 M. schmitti specimens (281 females; 415 males) were examined between July 2005 and October 2006. Length-frequency distribution (LFD) presented a peak at 660 mm total length (L) in both sexes, with females significantly larger in size than males. LWR was W = 1.36E−7 × L3.51 for females and W = 5.12E−6 × L2.93 in males. Of the captured females, 67% were mature, whereas 85% of captured males were mature. The smallest mature females and males were 455 and 495 mm L, respectively; largest immature females and males were 680 and 670 mm L. L50 and the confidence intervals (CI) were 597 mm (577–616) and 566 mm (553–580) for females and males, respectively. These figures are similar to those obtained from other populations in the area (34–41° S), although the L50 values were different from the Uruguayan outer shelf and populations further south. Fecundity ranged from 1 to 14 embryos per female (average = 6; SD = 3) and was positively correlated with female L. The results were compared with previous works comprising most of this species’ latitudinal distribution. This is the first research showing results of M. schmitti bottom-fixed gill-net artisanal fisheries. Different from industrial catches, this type of gear results in catches composed mainly of mature individuals (>80%), thus constituting an adequate scenario for sustainability of this endangered resource.

The Marvelous Tail ofLoddigesia mirabilis(Trochilidae)

ABSTRACT. Adult male Marvelous Spatuletails (Loddigesia mirabilis) have greatly specialized tail feathers (rackets) that are used in dramatic displays. We compared adult males' tail structure with that of immature males and females, and with that of related species, to determine the nature of adaptations in the tail. We provide the first detailed description and inference of the function of the rectricial bulb of the tail in hummingbirds. Metamorphic enlargement of the outer rectrices (pair 5) of male Marvelous Spatuletails first occurs before the body plumage is fully adult. The first two rackets apparently are grown sequentially; in subsequent, definitive molts they may be grown simultaneously. Vanes of the other postjuvenal rectrices (pairs 1–4) are small or rudimentary, and pairs 2–4 serve no aerodynamic function. However, the calami of these feathers contribute to the general structural complex of the rectricial bulb. Intrinsic muscles of the bulb govern spreading of the rackets, whereas extrinsic mu...

Characterization of antibodies for quantitative determination of spiggin protein levels in male and female three-spined stickleback (Gasterosteus aculeatus)

Spiggin is an adhesive glycoprotein produced in the kidney of sticklebacks during the breeding season and is subsequently secreted into the urinary bladder from where it is employed for nest building. Since the production of the protein has been shown to be under androgenic control, spiggin has been suggested to be a useful biomarker for androgenic substances in the environment. In this study, two polyclonal spiggin antibodies based on synthetic peptides and one polyclonal antibody directed against native spiggin have been characterized. The antibodies ability to identify spiggin was investigated by quantitative immunoassay. For both peptide antibodies the quantification range was determined to be between 1 and 80 ng spiggin and determination of renal spiggin levels from immature and mature males displayed a 15-fold increase in total spiggin content of the kidney resulting in a 6-fold increase in male kidney weight due to hypertrophy. The kidney somatic index (KSI) was found to correlate well with the total renal spiggin content and therefore it appears that KSI in sticklebacks could be used as an initial method to identify substances displaying androgenic effects. Furthermore, western blot analysis revealed that the polyclonal antibodies recognize different spiggin isoforms and that spiggin can be detected in the urinary bladder and kidney of both males and female sticklebacks. In order to develop a quantitative detection method for native spiggin it is necessary to produce a standard that can be used in a bioassay. Due to the adhesive and polymerization characteristics of spiggin the protein is difficult to use as a standard in bioassays. So far spiggin has been shown to exist in at least 14 isoforms, all of which contain polymerization domains. To overcome the solubility problem we have produced recombinant spiggin gamma, with only one polymerization domain, that can be expressed in E. coli. Western blot analysis demonstrated that the polyclonal antibodies were able to detect recombinant spiggin gamma protein in bacterial cell lysate, suggesting that it may be developed into a useful source of standard spiggin to be used for quantitative determination of androgen induced spiggin production in sticklebacks.

Age-dependent plasticity of sex pheromone response in the moth, Agrotis ipsilon: Combined effects of octopamine and juvenile hormone

Male moths use sex pheromones to find their mating partners. In the moth, Agrotis ipsilon, the behavioral response and the neuron sensitivity within the primary olfactory centre, the antennal lobe (AL), to sex pheromone increase with age and juvenile hormone (JH) biosynthesis. By manipulating the JH level, we previously showed that JH controls this age-dependent neuronal plasticity, and that its effects are slow (within 2 days). We hypothesized that the hormonal effect might be indirect, and one neuromodulator candidate, which might serve as a mediator, is octopamine (OA). Here, we studied the effects of OA and an OA receptor antagonist, mianserin, on behavioral and AL neuron responses of mature and immature males during stimulation with sex pheromone. Our results indicate that, although OA injections enhanced the behavioral pheromone response in mature males, OA had no significant effect on behavior in immature males. However, mianserin injections decreased the behavioral response in mature males. AL neuron sensitivity increased after OA treatment in immature males, and decreased after mianserin treatment in mature males. Determination of OA levels in ALs of immature and mature males did not reveal any difference. To study the possible interactive effects of JH and OA, the behavioral pheromone response was analyzed in JH-deprived mature males injected with OA, and in immature males injected with fenoxycarb, a JH agonist, and mianserin. Results show that both JH and OA are necessary to elicit a behavioral response of A. ipsilon males to sex pheromone.

Gene-expression signatures of Atlantic salmon’s plastic life cycle

How genomic expression differs as a function of life history variation is largely unknown. Atlantic salmon exhibits extreme alternative life histories. We defined the gene-expression signatures of wild-caught salmon at two different life stages by comparing the brain expression profiles of mature sneaker males and immature males, and early migrants and late migrants. In addition to life-stage-specific signatures, we discovered a surprisingly large gene set that was differentially regulated—at similar magnitudes, yet in opposite direction—in both life history transitions. We suggest that this co-variation is not a consequence of many independent cellular and molecular switches in the same direction but rather represents the molecular equivalent of a physiological shift orchestrated by one or very few master regulators.

Dispharynx nasuta (Nematoda: Acuariidae) em Guira guira e Crotophaga ani (Cuculiformes: Cuculidae) no Estado do Rio Grande do Sul, Brasil

Os nematóides do gênero Dispharynx (Railliet, Henry & Sisoff, 1912) parasitam aves de diversas ordens e têm sido estudados, principalmente, em aves de importância econômica devido às lesões que provocam no proventrículo dos hospedeiros. Dispharynx nasuta (Rudolphi, 1819) Stiles & Hassall, 1920 é registrado em duas espécies de Cuculiformes, anu-branco, Guira guira Gmelin, 1788 e anu-preto, Crotophaga ani Linnaeus, 1758, no Sul do Brasil. Entre 2005 e 2008 foram coletados e necropsiados 120 espécimes de G. guira e 120 espécimes de C. ani nos municípios de Cacequi, São Vicente do Sul e Jaguari, Rio Grande do Sul, Brasil. A prevalência de D. nasuta foi de 28,3% em G. guira e 26,7%, em C. ani, e a intensidade média de infecção foi de 8,81 (DP=18,41; Amplitude 1 - 82) helmintos/hospedeiro, em G. guira, e de 5,10 (DP=6,17; Amplitude 1 - 30) helmintos/hospedeiro, em C. ani. Já a abundância média de infecção foi de 2,28 (DP=10,02) helminto/hospedeiro, em G. guira, e de 1,32 (DP=3,82) helminto/hospedeiro em C. ani. Análise comparativa entre o sexo, a maturidade sexual e a estação do ano, para as duas espécies de aves, mostrou que em C. ani não ocorreram diferenças significativas com relação a qualquer dos parâmetros analisados. Em G. guira as fêmeas estavam mais parasitadas do que os machos (P=0,039); as fêmeas encontravam-se mais parasitadas no inverno (P=0,008); os machos, no verão (P=0,011); os machos jovens estavam mais parasitados do que os adultos (P=0,015). As lesões encontradas no proventrículo das aves parasitadas confirmaram o diagnóstico de hiperplasia adenomatóide do proventrículo com proventriculite granulomatosa. Esta comunicação amplia o número de espécies hospedeiras e a distribuição geográfica do nematóide D. nasuta.

Effects of aromatase inhibitors and different doses of testosterone on gonadotropins in one year old male Atlantic salmon ( Salmo salar)

The effects of different doses of testosterone (T), the aromatase inhibitors 1,4,6-androstatriene-3,17-dione (ATD) and 4-hydroxy-4-androstene-3,17-dione (4OH), and the combined treatment of T and ATD on luteinizing hormone (LH) and follicle-stimulating hormone (FSH) at the onset of puberty in juvenile Atlantic salmon males were investigated. T always increased pituitary LH. Also, ATD increased pituitary LH, though to a lesser extent than T. However, ATD combined with T diminished pituitary LH levels compared to T alone, indicating an aromatase-dependent positive feedback of T on LH in immature males. 4OH, which was less effective than ATD as an aromatase inhibitor, increased LH content. ATD treatment resulted in increased pituitary FSH levels, similar to those of mature controls. Positive effects of ATD on plasma FSH were found, indicating the presence of an aromatase-dependent negative feedback. The 4OH effects on FSH levels were inconsistent. T exerted both positive and negative effects on pituitary FSH and testes growth, depending on dose and season, with the positive effects being more pronounced with the low doses and the negative effects with the high doses. The treatment of T combined with ATD did not affect the positive effect of T alone on pituitary and plasma FSH, indicating the presence of an aromatase-independent positive feedback on FSH. There was a positive correlation between FSH and gonadosomatic index, especially during summer when gonadal development occurs.

A High-Speed Congenic Strategy Using First-Wave Male Germ Cells

BackgroundIn laboratory mice and rats, congenic breeding is essential for analyzing the genes of interest on specific genetic backgrounds and for analyzing quantitative trait loci. However, in theory it takes about 3–4 years to achieve a strain carrying about 99% of the recipient genome at the tenth backcrossing (N10). Even with marker-assisted selection, the so-called ‘speed congenic strategy’, it takes more than a year at N4 or N5.Methodology/Principal FindingsHere we describe a new high-speed congenic system using round spermatids retrieved from immature males (22–25 days of age). We applied the technique to three genetically modified strains of mice: transgenic (TG), knockin (KI) and N-ethyl-N-nitrosourea (ENU)-induced mutants. The donor mice had mixed genetic backgrounds of C57BL/6 (B6)∶DBA/2 or B6∶129 strains. At each generation, males used for backcrossing were selected based on polymorphic marker analysis and their round spermatids were injected into B6 strain oocytes. Backcrossing was repeated until N4 or N5. For the TG and ENU-mutant strains, the N5 generation was achieved on days 188 and 190 and the proportion of B6-homozygous loci was 100% (74 markers) and 97.7% (172/176 markers), respectively. For the KI strain, N4 was achieved on day 151, all the 86 markers being B6-homozygous as early as on day 106 at N3. The carrier males at the final generation were all fertile and propagated the modified genes. Thus, three congenic strains were established through rapid generation turnover between 41 and 44 days.Conclusions/SignificanceThis new high-speed breeding strategy enables us to produce congenic strains within about half a year. It should provide the fastest protocol for precise definition of the phenotypic effects of genes of interest on desired genetic backgrounds.

Características populacionais de Microphrys bicornutus (Brachyura, Mithracidae) no fital Halimeda opuntia (Chlorophyta, Halimedaceae), em área recifal submetida à visitação humana, em João Pessoa, Paraíba

Este trabalho teve como objetivos caracterizar e comparar a estrutura e a dinâmica populacional de Microphrys bicornutus Latreille, 1825 no fital Halimeda opuntia (Halimedaceae) coletado nas formações recifais de Picãozinho (submetida à visitação turística) e São Gonçalo (área controle), na costa de João Pessoa (Nordeste do Brasil), sob influência de fatores ambientais e do número de visitantes. Nas duas áreas de estudo as populações analisadas estiveram compostas por fêmeas e machos maduros e imaturos com significativa predominância de machos e de animais imaturos, freqüência de tamanho e períodos reprodutivos similares. O tamanho máximo dos exemplares, a freqüência de distribuição de tamanho e a razão sexual diferiram dos resultados obtidos para a espécie em outras latitudes e habitats. Dados de razão sexual evidenciam que independentemente do estágio de maturação, os machos apresentam predominância significativa (RS>1,0), e que a proporção de fêmeas diminui com o amadurecimento sexual. Sem sofrer influência da biomassa da alga, e da salinidade e temperatura da água, variações populacionais significativas foram associadas ao aumento de juvenis durante períodos chuvosos. A baixa densidade populacional e a maior desproporção da relação macho: fêmea em subárea de Picãozinho com maior fluxo de pessoas sugerem que estas variações podem ter sido induzidas pelo pisoteio das algas.

Early reproductive success, preceding bachelor ranks and their behavioural correlates in young Przewalski's stallions

Adult male dominance rank correlates with reproductive success in many mammalian species. Whether and how rank in immature males affects the number of offspring fathered later in life has rarely been investigated. Moreover, age, size and fighting skills all qualify as major intrinsic factors influencing rank, particularly in sexually dimorphic species, where they may be interdependent. In a socially natural herd of Przewalski's horses, a relatively monomorphic species, we explored (i) whether the dominance rank of young stallions living in a bachelor group was later associated with their reproductive success as young family holders, and (ii) whether higher ranking bachelors had a different behavioural profile to lower ranking ones in social interactions with peers. The stallions' behaviour was observed during their bachelor period, from which dominance ranks and their behavioural correlates were established. Foal paternities were determined through genetic analyses. The number of foals sired by stallions before 7 years of age correlated positively with their rank position when they lived in a bachelor group. Social play and mutual grooming were the most frequent interactions exchanged between bachelors, regardless of their rank. With age effects removed, higher ranking stallions did not show higher rates of physical aggression than lower ranking stallions, however, lower ranking stallions received more physical aggression from other stallions, and they engaged more often in stallion rituals than higher ranking stallions. This may show a propensity of subordinates for compromise rather than fighting.

Polistes dominulus (Hymenoptera, Vespidae) Larvae Show Different Cuticular Patterns According to their Sex: Workers Seem Not Use This Chemical Information

During reproductive phase, larvae of male and female are intermingled in nest of social wasps. Workers care for and feed larvae that gives them an opportunity to bias investment with respect to sex, or even to kill some larvae, if they can distinguish between immature males and females. Cuticular hydrocarbon (CHC) mixtures are the most studied cues for species, nestmate, and caste recognition in social Hymenoptera. In this study, we investigate the paper wasp Polistes dominulus to see if male and female larvae show different patterns of CHCs and if workers are able to discriminate between male and female larvae on this basis. We performed gas chromatography-mass spectrometry analysis on cuticular extracts of larvae, and then we genotyped them to assign sex. We found sex-based variation in CHC-profiles sufficient for discrimination. However, our behavioral assays do not support the view that adults discriminate between male and female larvae within nests.

<em>Leucon (Crymoleucon) rossi</em>, a new species (Crustacea: Cumacea: Leuconidae) from the shelf waters of the Ross Sea (Antarctica), with a key to the genus <em>Leucon</em> south of 60°S

A new leuconid cumacean, Leucon (Crymoleucon) rossi n. sp., is described from depths of 84 to 458 m in the Ross Sea off the Victoria Land coast. Leucon rossi n. sp. is distinguished from other members of the genus by a combination of characters including 1) a blunt, horizontally directed pseudorostrum without a distinctly protruding siphon; 2) strongly developed antennal notch; 3) entire dorsomedian margin of carapace appearing serrate, armed with 14 to 19 anteriorly curved spines in female (up to 21 in subadult males); 4) a small, but distinct, spine behind the frontal lobe; and 5) the uropodal peduncle slightly shorter than the exopod. After Leucon antarcticus Zimmer, 1907, L. rossi was the second most frequently occurring cumacean in the samples collected off Victoria Land. Statistical analyses showed significant differences in the proportion of carapace length and height of adult (all incubating in the present study) and immature females compared to immature males; no adult males were available for study.

Re‐examining the relationship between sexual maturation and age of response to methyl eugenol in males of the oriental fruit fly

AbstractMales of the oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), are strongly attracted to, and feed voraciously on, methyl eugenol (ME) and use metabolites of this chemical to synthesize their sex pheromone. Previously, Wong et al. (1989) proposed that B. dorsalis males were attracted to ME even before attaining sexual maturity. However, their interpretation is possibly confounded by the fact that, in monitoring age‐related mating readiness, males were presented with equal‐aged females. As a result, if females mature more slowly than males, the age of male sexual maturation may have been overestimated, which may have accounted for the discrepancy observed between male age of ME responsiveness and mating activity. Here, we re‐examined the relationship between male age and mating readiness by comparing male mating activity when presented with same‐aged females vs. sexually mature females. In addition, we measured the age‐dependent response of B. dorsalis males to ME by recording (i) capture in ME‐baited traps, and (ii) feeding duration on ME‐containing paper discs. Our data support the conclusion of Wong et al. (1989) that B. dorsalis males show attraction to, and feed on, ME before attaining sexual maturity, but suggest that a marked difference in ME response and mating activity exists over a shorter age interval than indicated by Wong et al. (1989). Early attraction to, but not ingestion of, ME was related to accelerated sexual maturation. Unexpectedly, ingestion of ME by sexually immature males did not boost their mating success in trials conducted 10 days after feeding on the lure.

Survival Rates of the California Sea Lion,Zalophus californianus, in Mexico

California sea lions (Zalophus californianus) in the Gulf of California have declined by 20% over the past 2 decades. The lack of data on life-history parameters for this species has limited the development of demographic models to assess the status of this population. We estimated age- and sex-specific annual survival probabilities for California sea lions using resighting data on 5 pup cohorts from 1981 to 2006. We modeled apparent survival and resighting probability using age-class, sex, and time as potential explanatory variables. Apparent survival rates varied for different age- and sex-classes. Only survival of pups varied by year (from 0.556 to 0.998). Survival was the same for immature males and females (0.90), but differed by sex for young (males = 0.90, females = 0.97) and old (males = 0.75, females = 0.91) adults. Resighting probabilities varied by time, age-class, and sex. Resighting probabilities were higher for females than for males, and lowest for juveniles. The survival estimates presented here provide practical insight into understanding age- and sex-specific survival rates for California sea lions.