Lifetime survival rates and senescence in northern elephant seals

The aim of this study was to extend 40 yr of prior demographic work on northern elephant seals (Mirounga angustirostris) at Año Nuevo, California, by including the oldest animals. We used a Bayesian mark‐recapture analysis to estimate lifelong survival and lifespan of a cohort of 372 weaned pups branded in 1985–1987 and resighted until 2008. Annual survival probability of females averaged 86.3%/yr at ages 5–16, then declined until age 21, the age of the oldest female. Male survival was lower, averaging 67.7%/yr from age 1 to age 15, the age of the oldest male. Northern elephant seal females in the expanding population at Año Nuevo live longer than southern elephant seal females (M. leonina) at colonies whose populations are declining. This comparison suggests that high survival of females is a key factor in population growth.     

Female competition and reproductive success in northern elephant seals

The probability of weaning a healthy pup increases with age in female northern elephant seals, Mirounga angustirostris. On Año Nuevo Island, California, weaning success among ‘prime’ females, those 6 years of age or older, was more than double that of ‘young’ females, those 3 to 5 years old. Prime females were better mothers than young females because of superior size, higher social dominance, and greater maternal experience; they were more likely to mate with high-ranking males and gave birth at an optimal time and place, circumstances that maximized the probability that their pups would survive, develop, and reproduce. The competitive advantage of prime-age mothers over younger ones was greatest when female and pup density was high. Young females improved their chances of reproducing successfully by emigrating from crowded harems and establishing new colonies.     

PINUS × CRITCHFIELDII,A LATE PLEISTOCENE HYBRID PINE FROM COASTAL SOUTHERN CALIFORNIA

Fossil cones buried in an old landslide at San Clemente are dated at 30,000–34,000 BP (years before present). They generally resemble cones of the natural hybrid Pinus radiata × P. attenuata at Año Nuevo, and also the artificial hybrid P. × attenuradiata. But differences in cone shape, size, and apophyses suggest that the fossil P. × critchfieldii Axelrod and T. G. Hill represents a hybrid of populations of P. radiata and P. attenuata then in coastal southern California. This agrees with population differences between these species in central and southern California during the Pleistocene. Regional comparisons of Late Pleistocene floras indicate that at San Clemente mean annual rainfall was about 580–635 mm, or twice that of today, mean annual temperature was about 2.5 C cooler (13.5 vs. 16.0 C), the mean monthly range was lower (5.9 vs. 7.7 C), the growing season was about 40 days shorter (170 vs. 210 days), and equability was higher (M 72 vs. M 67). Forest was replaced by coastal sage scrub and grassland along the San Clemente coast as drier, warmer climate developed after 12,000 BP.     

Ultrasonic Vocalizations of Male Mice Differ among Species and Females Show Assortative Preferences for Male Calls

Male house mice (Mus musculus) emit ultrasonic vocalizations (USVs) during courtship, which attract females, and we aimed to test whether females use these vocalizations for species or subspecies recognition of potential mates. We recorded courtship USVs of males from different Mus species, Mus musculus subspecies, and populations (F1 offspring of wild-caught Mus musculus musculus, Mus musculus domesticus (and F1 hybrid crosses), and Mus spicilegus), and we conducted playback experiments to measure female preferences for male USVs. Male vocalizations contained at least seven distinct syllable types, whose frequency of occurrence varied among species, subspecies, and populations. Detailed analyses of multiple common syllable types indicated that Mus musculus and Mus spicilegus could be discriminated based on spectral and temporal characteristics of their vocalizations, and populations of Mus musculus were also distinctive regardless of the classification model used. Females were able to discriminate USVs from different species, and showed assortative preferences for conspecific males. We found no evidence that females discriminate USVs of males from a different subspecies or separate populations of the same species, even though our spectral analyses identified acoustic features that differ between species, subspecies, and populations of the same species. Our results provide the first comparison of USVs between Mus species or between Mus musculus subspecies, and the first evidence that male USVs potentially facilitate species recognition.     

DYNAMIC RESPONSE ANALYSIS. III. A CONSISTENCY FILTER AND APPLICATION TO FOUR NORTHERN ELEPHANT SEAL COLONIES

Dynamic response analysis, a technique for determining stock size relative to the maximum net productivity level (MNPL), was applied to northern elephant seal populations from the South Farallon Islands, Año Nuevo Island, San Nicolas Island and San Miguel Island. Pup counts were used as indices of population size. The application of dynamic response analysis presented here involved some methodological innovations. We present a moving interval method which involves calculating separate dynamic response analyses for intervals of various lengths ranging from four counts to the total number available for the colony. The sign of the second order polynomial regression coefficient computed from a particular interval was used to indicate the colony's apparent status (relative to its MNPL, += above MNPL, - = below MNPL) on that interval. Consistency in the sign of the second order coefficient, as the interval was moved along the trajectory, was used to determine the minimum reliable interval size. Each colony exhibited growth similar to that of a population below its MNPL. These results are consistent with recent natural history observations at San Nicolas, San Miguel and the South Farallon islands. Natural history observations at Año Nuevo Island suggest that the colony there is now at equilibrium. Thus, if our results from dynamic response analysis of the Ano Nuevo colony are correct, it appears that the MNPL may be close to the carrying capacity for these animals.     

Long distance breeding dispersal of a southern elephant seal

Southern elephant seals range extensively during regular foraging excursions. Despite this they are highly philopatric and long range dispersal is rare. At Gough Island, southern Atlantic Ocean, we observed a breeding adult male elephant seal during September 2009, which had been tagged on its natal beach at Marion Island, southern Indian Ocean, in November 1998. The individual was resighted only once on Marion Island, 6 months after tagging. This 3,860 km movement represents dispersal (and likely gene flow) between distinct populations from different elephant seal geographical provinces. Given the polygynous breeding system of this species, the presence of this single male may have a disproportionate genetic effect on the small number of southern elephant seals breeding at Gough Island.     

Growth and body size in populations of mink frogs Rana septentrionalis from two latitudes

Age, longevity, and growth in mink frogs Rana septentrionalis from two latitudes in Quebec, Canada, were assessed by skeletochronological and back-calculation methods in order to document proximate causes for intraspecific variations in adult body size. In both study sites, females grew faster and were on average 11% larger than males. Mean age and maximal longevity were significantly higher in females than in males only in the southern populations. There was thus an interpopulation difference in the relative contribution of age and growth to sexual size dimorphisms. Sex-ratio also favored females (males sulfering higher mortality) only in the southern populations. Specimens from the northern population had higher mean ages (but not higher longevities) and were 17% larger than specimens from the southern populations. Annual growth rate appeared similar at the two study sites despite a shorter growing season at the northern locality. Maturity was reached by both sexes after 1 yr of post-metamorphic life (PML) in the southern populations but after 2 yr of PML in the northern population. There are indications that tadpoles metamorphose at larger body size at the northern locality after a prolonged larval period. It is concluded that growth rate, delayed maturity, greater mean ages, and eventually size at transformation, all contribute to the larger size of adult mink frogs at northern localities.     

Sex determination without the Y Chromosome in two Japanese rodents Tokudaia osimensis osimensis and Tokudaia osimensis spp.

Both males and females of the species of spinous country-rats (Tokudaia osimensis osimensis, T. o. o., Rodentia: Muridae), which live on Amami Oshima Island, a southern Japanese island, have 25 chromosomes. Another species of spinous country-rats (Tokudaia osimensis spp., T. o. spp., which live on Tokunoshima Island 40 km south of Amami Oshima Island, also have an odd number of chromosomes, 45. Karyotypes of males and females by the G-band method were indistinguishable in both populations. The lesser number of chromosomes (25) of T. o. o. is likely to be a result of Robertsonian fusions of 45 chromosomes of T. o. spp. that seem to be the offspring of another spinous country-rat Tokudaia osimensis muenninki (T. o. m.), which live on Okinawa Island and have 44 chromosomes including the X and Y Chrs. The lengths of the non-paired, putative X-Chr of T. o. o. and T. o. spp. occupied roughly 3.2% and 1.7% of the total lengths, respectively, hinting at translocation or exchange of a part of the X Chr and thus in violation of Ohno's Law. Southern blot analysis with murine Sry as a probe indicated that these two animals do not have Sry. When Zfx from T. o. spp. was used as a probe, both males and females of T. o. o. and T. o. spp. showed two bands, suggesting possible translocation of Zfy from the Y Chr. Comparison of physical characteristics, constituents of chromosomes, and sex-determination methods of these three Tokudaia country-rat populations suggests that each is endemic to each island and constitutes an independent species. These specialized species would provide us with clues to elucidate the mechanisms of primary sex determination and karyotype evolution in mammals. Received: 2 June 2000 / Accepted: 24 August 2000     

The behaviour of Abudefduf zonatus (Pisces,pomacentridae) at Heron Island,Great Barrier Reef

Social organization and reproductive behaviour of Abudefduf zonatus were studied at Heron Island, Great Barrier Reef. This species is closely associated with the sand and coral substrate of the inner reef flat zone. Territorial, clustering, nest-digging, breeding and parental care behaviours are described. Mature males maintain territories for several weeks or longer around empty clam shells in which periodic spawning occurs. Females and sub-adult males hold territories interspersed among those of adult males. No pair bonds are formed, and eggs are guarded only by males. Breeding is roughly synchronized among fish of one area. Clustering behaviour may contribute to breeding syndrony in local populations.     

Climate adaptation is not enough: warming does not facilitate success of southern tundra plant populations in the high Arctic

Rapidly rising temperatures are expected to cause latitudinal and elevational range shifts as species track their optimal climate north and upward. However, a lack of adaptation to environmental conditions other than climate – for example photoperiod, biotic interactions, or edaphic conditions – might limit the success of immigrants in a new location despite hospitable climatic conditions. Here, we present one of the first direct experimental tests of the hypothesis that warmer temperatures at northern latitudes will confer a fitness advantage to southern immigrants relative to native populations. As rates of warming in the Arctic are more than double the global average, understanding the impacts of warming in Arctic ecosystems is especially urgent. We established experimentally warmed and nonwarmed common garden plots at Alexandra Fiord, Ellesmere Island in the Canadian High Arctic with seeds of two forb species (Oxyria digyna and Papaver radicatum) originating from three to five populations at different latitudes across the Arctic. We found that plants from the local populations generally had higher survival and obtained a greater maximum size than foreign individuals, regardless of warming treatment. Phenological traits varied with latitude of the source population, such that southern populations demonstrated substantially delayed leaf‐out and senescence relative to northern populations. Our results suggest that environmental conditions other than temperature may influence the ability of foreign populations and species to establish at more northerly latitudes as the climate warms, potentially leading to lags in northward range shifts for some species.     

DIFFERENCES IN FORAGING LOCATION OF MEXICAN AND CALIFORNIA ELEPHANT SEALS: EVIDENCE FROM STABLE ISOTOPES IN PUPS

Female northern elephant seals, Mirounga angustirostris, from Año Nuevo (AN) in central California feed offshore in mid‐latitude waters (40°–55°N). Migratory patterns and foraging locations of seals from Mexico are unknown. Rookeries on San Benitos (SB) islands in Baja California Sur, Mexico, are ～1,170 km south of AN. Although the colonies are similar in size, seals from SB begin breeding earlier and have an earlier breeding birthing peak than seals from AN. To determine if the foraging location of seals from Mexico was similar to that of seals from California, we measured δ¹³C and δ¹⁵N values in the hair of 48 suckling pups at SB and 37 from AN, assuming that their isotopic signatures reflected those of mothers' milk, their exclusive diet. The mean δ¹³C and δ¹⁵N values for SB pups (?16.1‰± 0.9‰ and 17.7‰± 0.9‰, respectively) were significantly higher than those for AN pups (?17.6‰± 0.4‰ and 15.6‰± 1.0‰, respectively). From data on environmental isotope gradients and known behavior of SB and AN populations, we hypothesize that the isotope differences are due to females in the SB colony foraging ～8° south of seals from AN. This hypothesis can be tested by deployment of satellite tags on adult females from the SB colony.     

First record of the Late Cretaceous giant bird Gargantuavis philoinos from the Iberian Peninsula

Gargantuavis philoinos is a large terrestrial bird, initially described from several bones (synsacrum, cervical vertebra, femora) discovered in the Late Cretaceous deposits of southern France. The synsacrum described here comes from the late Campanian (Late Cretaceous) site of Laño, in north-western Spain, and is similar in all respects to the other synsacra of Gargantuavis philoinos described from France. This is therefore the first specimen attributed to this species to be reported outside France. This find increases the diversity of the fossil assemblage from Laño and the geographical distribution of this bird, which existed on the Ibero-Armorican island, which included southern France and the Iberian Peninsula, during the Late Cretaceous.     

Reductions in the dietary niche of southern sea otters (Enhydra lutris nereis) from the Holocene to the Anthropocene

The sea otter (Enhydra lutris) is a marine mammal hunted to near extinction during the 1800s. Despite their well‐known modern importance as a keystone species, we know little about historical sea otter ecology. Here, we characterize the ecological niche of ancient southern sea otters (E. lutris nereis) using δ¹³C analysis and δ¹⁵N analysis of bones recovered from archaeological sites spanning ~7,000 to 350 years before present (N = 112 individuals) at five regions along the coast of California. These data are compared with previously published data on modern animals (N = 165) and potential modern prey items. In addition, we analyze the δ¹⁵N of individual amino acids for 23 individuals to test for differences in sea otter trophic ecology through time. After correcting for tissue‐specific and temporal isotopic effects, we employ nonparametric statistics and Bayesian niche models to quantify differences among ancient and modern animals. We find ancient otters occupied a larger isotopic niche than nearly all modern localities; likely reflecting broader habitat and prey use in prefur trade populations. In addition, ancient sea otters at the most southerly sites occupied an isotopic niche that was more than twice as large as ancient otters from northerly regions. This likely reflects greater invertebrate prey diversity in southern California relative to northern California. Thus, we suggest the potential dietary niche of sea otters in southern California could be larger than in central and northern California. At two sites, Año Nuevo and Monterey Bay, ancient otters had significantly higher δ¹⁵N values than modern populations. Amino acid δ¹⁵N data indicated this resulted from shifting baseline isotope values, rather than a change in sea otter trophic ecology. Our results help in better understanding the contemporary ecological role of sea otters and exemplify the strength of combing zooarchaeological and biological information to provide baseline data for conservation efforts.     

Sex-linked and autosomal microsatellites provide new insights into island populations of the tammar wallaby

The emerging availability of microsatellite markers from mammalian sex chromosomes provides opportunities to investigate both male- and female-mediated gene flow in wild populations, identifying patterns not apparent from the analysis of autosomal markers alone. Tammar wallabies (Macropus eugenii), once spread over the southern mainland, have been isolated on several islands off the Western Australian and South Australian coastlines for between 10 000 and 13 000 years. Here, we combine analyses of autosomal, Y-linked and X-linked microsatellite loci to investigate genetic variation in populations of this species on two islands (Kangaroo Island, South Australia and Garden Island, Western Australia). All measures of diversity were higher for the larger Kangaroo Island population, in which genetic variation was lowest at Y-linked markers and highest at autosomal markers (θ=3.291, 1.208 and 0.627 for autosomal, X-linked and Y-linked data, respectively). Greater relatedness among females than males provides evidence for male-biased dispersal in this population, while sex-linked markers identified genetic lineages not apparent from autosomal data alone. Overall genetic diversity in the Garden Island population was low, especially on the Y chromosome where most males shared a common haplotype, and we observed high levels of inbreeding and relatedness among individuals. Our findings highlight the utility of this approach for management actions, such as the selection of animals for translocation or captive breeding, and the ecological insights that may be gained by combining analyses of microsatellite markers on sex chromosomes with those derived from autosomes.     

Inter-population differences in diving behaviour of adult male southern elephant seals (Mirounga leonina)

Access to different environments may lead to inter-population behavioural changes within a species that allow populations to exploit their immediate environments. Elephant seals from Marion Island (MI) and King George Island (KGI) (Isla 25 de Mayo) forage in different oceanic environments and evidently employ different foraging strategies. This study elucidates some of the factors influencing the diving behaviour of male southern elephant seals from these populations tracked between 1999 and 2002. Mixed-effects models were used to determine the influence of bathymetry, population of origin, body length (as a proxy for size) and individual variation on the diving behaviour of adult male elephant seals from the two populations. Males from KGI and MI showed differences in all dive parameters. MI males dived deeper and longer (median: 652.0?m and 34.00?min) than KGI males (median: 359.1?m and 25.50?min). KGI males appeared to forage both benthically and pelagically while MI males in this study rarely reached depths close to the seafloor and appeared to forage pelagically. Model outputs indicate that males from the two populations showed substantial differences in their dive depths, even when foraging in areas of similar water depth. Whereas dive depths were not significantly influenced by the size of the animals, size played a significant role in dive durations, though this was also influenced by the population that elephant seals originated from. This study provides some support for inter-population differences in dive behaviour of male southern elephant seals.     

The effects of El Niño–La Niña on reproductive parameters of elephant seals feeding in the Bellingshausen Sea

Aim To assess the impacts of El Niño–La Niña events on the pup weaning mass and diet of female southern elephant seals (Mirounga leonina) feeding in the Bellingshausen Sea, Antarctica, and to understand the ecological processes that drive these impacts. Location Atlantic southern elephant seal weaning mass and diet were measured at King George Island (62º14′ S, 58º30′ W). Feeding areas for pregnant female seals from King George Island are located west of Alexander Island in the Bellingshausen Sea. Methods Data on weaning mass were collected between 1985 and 1994 during the breeding season (September–November). Moulting females were anaesthetized and cephalopod beaks were isolated and identified from stomach contents obtained from stomach lavages. Sea‐surface temperature anomaly (SSTA) data for the ‘El Niño 3.4’ geographical region (5º N–5º S, 120º W–170º W) were used to define El Niño–Southern Oscillation (ENSO) event years (grouped as El Niño, La Niña and Neutral) as well as the strength of each ENSO event year. Using data from the US National Center for Environmental Prediction, temperature, sea ice concentration and atmospheric pressure anomalies in the Bellingshausen Sea were calculated from March to August, corresponding to the feeding period of pregnant female seals. Results Positive temperature anomalies and negative pressure anomalies in the Bellingshausen Sea were observed during La Niña years and negative temperature anomalies and positive pressure anomalies during El Niño years. These data correlate with sea ice concentration anomalies, which are highly negative during La Niña years and highly positive during El Niño years. Warm temperature conditions in the Bellingshausen Sea during La Niña years are strongly related to both higher weaning mass in elephant seals and to an increase in squid beaks in the stomach contents of females. Main conclusions It is possible that higher elephant seal weaning masses in La Niña years correlate with warmer waters in the Bellingshausen Sea leading to the rapid growth of squid and their more frequent descents to depths frequented by elephant seals. This results in increased predation by pregnant females, leading to a greater mass among weaned pups. This hypothesis may guide future research about interactions between climate and the marine biosphere.     

Divergence of Acoustic Signals in a Widely Distributed Frog: Relevance of Inter-Male Interactions

Divergence of acoustic signals in a geographic scale results from diverse evolutionary forces acting in parallel and affecting directly inter-male vocal interactions among disjunct populations. Pleurodema thaul is a frog having an extensive latitudinal distribution in Chile along which males'' advertisement calls exhibit an important variation. Using the playback paradigm we studied the evoked vocal responses of males of three populations of P. thaul in Chile, from northern, central and southern distribution. In each population, males were stimulated with standard synthetic calls having the acoustic structure of local and foreign populations. Males of both northern and central populations displayed strong vocal responses when were confronted with the synthetic call of their own populations, giving weaker responses to the call of the southern population. The southern population gave stronger responses to calls of the northern population than to the local call. Furthermore, males in all populations were stimulated with synthetic calls for which the dominant frequency, pulse rate and modulation depth were varied parametrically. Individuals from the northern and central populations gave lower responses to a synthetic call devoid of amplitude modulation relative to stimuli containing modulation depths between 30–100%, whereas the southern population responded similarly to all stimuli in this series. Geographic variation in the evoked vocal responses of males of P. thaul underlines the importance of inter-male interactions in driving the divergence of the acoustic traits and contributes evidence for a role of intra-sexual selection in the evolution of the sound communication system of this anuran.     

Birth seasonality and offspring production in threatened neotropical primates related to climate

Given the threatened status of many primate species, the impacts of global warming on primate reproduction and, consequently, population growth should be of concern. We examined relations between climatic variability and birth seasonality, offspring production, and infant sex ratios in two ateline primates, northern muriquis, and woolly monkeys. In both species, the annual birth season was delayed by dry conditions and El Niño years, and delayed birth seasons were linked to lower birth rates. Additionally, increased mean annual temperatures were associated with lower birth rates for northern muriquis. Offspring sex ratios varied with climatic conditions in both species, but in different ways: directly in woolly monkeys and indirectly in northern muriquis. Woolly monkeys displayed an increase in the proportion of males among offspring in association with El Niño events, whereas in northern muriquis, increases in the proportion of males among offspring were associated with delayed onset of the birth season, which itself was related, although weakly, to warm, dry conditions. These results illustrate that global warming, increased drought frequency, and changes in the frequency of El Niño events could limit primate reproductive output, threatening the persistence and recovery of ateline primate populations.     

Acoustic characterization of ultrasonic vocalizations by a nocturnal primate Tarsius syrichta

This preliminary study characterizes the ultrasonic vocalizations produced by Philippine tarsiers, Tarsius syrichta. Data were collected at the Philippine Tarsier Foundation Sanctuary in Corella, Bohol, Philippines, from July through October 2010. Recordings were made on a Wildlife Acoustics Ultrasonic Song Meter 2 BAT from 29 wild, free-living adult resident T. syrichta (23 females and six males). A total of 10,309 USVs were recorded. These vocalizations fell into three main categories: chirps, twitters, and whistles. Chirps were the most frequent, followed by twitters and whistles. Whereas chirps and twitters were emitted by both male and female Philippine tarsiers, whistles were only emitted by adult males. Given that vocalizations reported in this study were exclusively recorded during capture and handling, it is very likely that these vocalizations function as distress calls. However, as the long whistle was only given by adult males who were captured at the same time as the female or the group’s infant, the function of the long whistle might be slightly different than the function of the other relatively lower-frequency USVs.     

Ethological and phenotypic divergence in insular fire salamanders: diurnal activity mediated by predation?

Phenotypic divergence can occur through both local adaptations and phenotypic plasticity in response to particular environmental pressures. Holocene land-bridge islands harbor recent isolated populations that offer an excellent natural framework to study the microevolutionary processes involved in rapid or ongoing phenotypic shifts. Two insular populations (Ons and San Martiño) of Salamandra salamandra in NW Iberian Peninsula exemplify these phenotypic shifts with a rapid evolutionary transition in reproductive mode and genetic differentiation since their isolation ca. 8000 years ago. We evaluate parallel phenotypic changes in body size and behavior. In particular, we (1) collected observational fieldwork data during diurnal and nocturnal transects in both islands for over a decade (2004–2016); (2) investigated the climatic conditions associated to fire salamanders’ activity; (3) compared physical condition between insular and mainland populations; and (4) used plasticine models and camera trapping to identify potential predators that might cause the observed diurnal activity in San Martiño Island. Our 13-year-long study shows that salamanders from San Martiño show mainly diurnal activity and are significantly smaller than salamanders from Ons and nearby continental populations. Overall, we present an exceptional case of behavior and phenotypic differentiation of an insular population of fire salamanders and suggest that this unusual behavior in the small population of San Martiño might be triggered by a response to predator pressure exerted by a dense population of Rattus rattus.