Rafael A. Martínez-Díaz, Mónica Beatriz Martella, Joaquín Luis Navarro, Francisco Ponce-Gordo, Gastrointestinal parasites in greater rheas (Rhea americana) and lesser rheas (Rhea pennata) from Argentina, Veterinary Parasitology, Volume 194, Issue 1, 1 May 2013, Pages 75-78, ISSN 0304-4017, 10.1016/j.vetpar.2012.12.021.
Few data exist on the parasites of ratites, especially from regions within their natural range. It is only recently that extensive studies on the parasites of ostriches (Struthio camelus) have been published, mainly from European countries where commercial farming has expanded. Two species of ratites are native in South America: the lesser rhea also known as Darwin’s rhea (Rhea pennata) and the greater rhea (Rhea americana). Both species are considered near threatened by the IUCN and are included in the CITES’ Appendices I and II, respectively. Parasitological studies have conservation implications, as they allow us to assess the risk of transmission of pathogens from farmed ratites to wild populations. In this study 92 faecal samples from greater rheas and 55 faecal samples from lesser rheas from different localities in Argentine were analyzed to determine their gastrointestinal parasites. In greater rheas the protozoa (Balantidium coli-like and Entamoeba spp.) and helminths (Fasciola hepatica and Deletrocephalus spp.). The protozoa had not previously been cited as parasites of greater rheas in South America. Cysts and/or trophozoites of B. coli-like were found in 16.3% of the samples, while the prevalence of the remaining parasites was below 10%. Lesser rheas harbored the protozoa B. coli-like, Entamoeba spp. and Chilomastix spp. as well as F. hepatica and nematode eggs and larvae. B. coli-like cysts were found in 20.0% of the samples, while the prevalence of the other parasites remained below 5%. Some of them had not been cited as infecting lesser rheas yet.
Pernilla Foyer, Erik Wilsson, Dominic Wright, Per Jensen, Early experiences modulate stress coping in a population of German shepherd dogs, Applied Animal Behaviour Science, Available online 20 April 2013, ISSN 0168-1591, 10.1016/j.applanim.2013.03.013.
Early experiences may alter later behavioural expressions in animals and these differences can be consistent through adulthood. In dogs, this may have a profound impact on welfare and working ability and, it is therefore interesting to evaluate how experiences during the first weeks of life contribute to shaping the long-term behaviour. We analysed data from 503 dogs from 105 litters, bred at the Swedish Armed Forces Dog Kennel. For each dog, the data comprised information on dam and sire, sex, litter size, sex ratio of litter, date of birth, and weight at birth, and at 10 days of age. Between the ages of 377 and 593 days, the dogs were tested in a temperament test, assessing their suitability as working dogs. The behaviour test comprised 12 different sub-tests, and was scored on a behavioural rating scale. A principal component analysis showed that the test performance could largely be attributed to four principal components (explaining 55.7% of variation), labelled Confidence, Physical Engagement, Social Engagement and Aggression. We analysed the effects of the different early life variables and sex on the principal component scores (PC scores) using linear modelling. PC scores on Confidence were affected by parity, sex and litter size, and Physical Engagement was affected by parity, growth rate, litter size and season of birth. Social Engagement was affected by growth rate and sex, and Aggression was affected by sex. Some of these effects disappeared when they were combined into a single linear model, but most of them remained significant also when controlling for collinearity. The results suggest that the early environment of dogs have long-lasting effects on their behaviour and coping styles in a stressful test situation and this knowledge can be used in the work with breeding of future military or police working dogs.
Sandra D. Starke, Kirsty J. Raistrick, Stephen A. May, Thilo Pfau, The effect of trotting speed on the evaluation of subtle lameness in horses, The Veterinary Journal, Available online 20 April 2013, ISSN 1090-0233, 10.1016/j.tvjl.2013.03.006.
Equine lameness is a significant and challenging part of a veterinarian’s workload, with subtle lameness inherently difficult to assess. This study investigated the influence of trotting speed on perceived and measured changes in movement asymmetry. Ten sound to mildly lame horses were trotted at a ‘slow’, ‘preferred’ and ‘fast’ speed on a hard surface, both on a straight line and in a circle on left and right reins. Video recordings of the horses were visually assessed by six experienced equine clinicians. Vertical movement of head, withers and pelvis was derived from inertial sensor data and several features calculated.
On the straight line, more horses were subjectively declared sound at higher speeds, whilst different objective asymmetry measures showed only slight and inconsistent changes. On the circle, speed had no significant effect on the subjective assessment, with an increase in objectively measured asymmetry at higher speeds possibly balanced by a decrease in sensitivity of the observers for this asymmetry. Horses visually examined for subtle lameness on the straight should therefore be evaluated at a slow speed. Trotting speed should be consistent on repeated occasions, especially during objective gait analysis on the circle, to avoid the interaction of treatment effects and speed effects.
Robin L. Vaughn-Hirshorn, Elisa Muzi, Jessica L Richardson, Gabriella J. Fox, Lauren N. Hansen, Alyce M. Salley, Kathleen M. Dudzinski, Bernd Würsig, Dolphin underwater bait-balling behaviors in relation to group and prey ball sizes, Behavioural Processes, Available online 19 April 2013, ISSN 0376-6357, 10.1016/j.beproc.2013.04.003.
We characterized dusky dolphin (Lagenorhynchus obscurus) feeding behaviors recorded on underwater video, and related behaviors to variation in prey ball sizes, dolphin group sizes, and study site (Argentina vs. New Zealand, NZ). Herding behaviors most often involved dolphins swimming around the side or under prey balls, but dolphins in Argentina more often swam under prey balls (48% of passes) than did dolphins in NZ (34% of passes). This result may have been due to differences in group sizes between sites, since groups are larger in Argentina. Additionally, in NZ, group size was positively correlated with proportion of passes that occurred under prey balls (p<0.001). Prey-capture attempts most often involved capturing fish from the side of prey balls, but dolphins in Argentina more often swam through prey balls (8% of attempts) than did dolphins in NZ (4% of attempts). This result may have been due to differences in prey ball sizes between sites, since dolphins fed on larger prey balls in Argentina (74 m2) than in NZ (maximum 33 m2). Additionally, in NZ, dolphins were more likely to swim through prey balls to capture fish when they fed on larger prey balls (p=0.025).
A. A. Barnett, B. Ronchi-Teles, T. Almeida, A. Deveny, V. Schiel-Baracuhy, W. Souza-Silva, W. Spironello, C. Ross, A. MacLarnon
Arthropod Predation by a Specialist Seed Predator, the Golden-backed Uacari (Cacajao melanocephalus ouakary, Pitheciidae) in Brazilian Amazonia
International Journal of Primatology, April 2013
Morphological adaptations related to food processing generally reflect those elements of the diet that represent the greatest biomechanical challenge or that numerically dominate the diet. However, in periods of the annual cycle when the availability of such foods is low, items to which a species has low apparent morphological adaptation may be included in the diet. Here we test the responses of a diet-specialist primate to limitations in the supply of the resource it is specialized to exploit. Uacaris are primarily predators of immature seeds, in seasonally flooded forests in Amazonian Brazil, and have dental specializations to open hard-shelled fruits. We investigated the importance of arthropods in the diet of golden-backed uacaris (Cacajao melanocephalus ouakary), examining their seasonal importance in the uacari diet, and the ways C. m. ouakary used to access them. Using scan and ad libitum sampling of feeding and phenology from botanical study plots to assess fruit availability, we conducted an 18-mo study in Jaú National Park, Amazonas State, Brazil. We recorded arthropod predation 298 times, with Cacajao melanocephalus ouakary feeding on 26 invertebrate taxa in ≥11 families and 9 different orders. Uacaris extracted wood-boring beetles dentally from rotting wood and smaller larvae from twigs, stems, and petioles, but this food class did not predominate. This food class (encapsulated foods) constituted 23.4 % of the arthropod records. The majority of arthropod food items were either manually removed from substrates (ants, beetle larvae, caterpillars, fulgorid bugs, grasshoppers, mayflies, spiders, termites, wasps, and a whip-scorpion) or plucked from the air (volant Lepidoptera). Uacaris appeared to avoid toxic caterpillars. Insectivory was most frequent when fruit and seeds were least available. Arthropods seem to be seasonally important to this primate, supplementing or making up for shortfalls in the hard fruits and immature seeds for which uacaris have highly developed dental, and possibly intestinal, adaptations.
Michael L Domeier, Nicole Nasby-Lucas
Two-year migration of adult female white sharks (Carcharodon carcharias) reveals widely separated nursery areas and conservation concerns
Animal Biotelemetry, April 2013
Satellite tagging programs have provided detailed information about the migratory patterns of northeastern Pacific white sharks, revealing a seasonal migration between a vast offshore region and coastal aggregation sites. Although adult males undergo annual round-trip migrations, photo-identification programs have noted that sexually mature females may only visit coastal aggregation sites once every 2 years, a behavior that is presumably linked to an estimated 18-month gestation period. The whereabouts of females during their full 2-year migration were previously unknown, because of the limited battery capacity of satellite pop-up tags.
Through the use of satellite-linked radio-telemetry tags with multi-year tracking capability, we describe the 2-year migratory pattern for four mature female white sharks tagged at Guadalupe Island, Mexico. The 2-year migration comprised four phases: 1) an Offshore Gestation Phase (which had an average duration of 15.5 months; 2) a Pupping Phase, which occurred along the Mexican coast between the months of April and August; 3) a Pre-Aggregation Phase (when the females were in transition between the Pupping Phase and Guadalupe Island; and 4) the Guadalupe Island Aggregation Phase, which began when the mature females arrived at Guadalupe Island between late September and early October.
Long-term satellite tracking of mature female white sharks highlighted the connectivity between a single presumed mating site at Guadalupe Island, and two widely separated pupping sites along the Mexican coast. The Offshore Gestation Phase provided evidence that the females remained offshore for up to 16 months during their 2-year migration cycle. The Pupping Phase along the Mexican coast coincided with the seasonal presence of young-of-the-year white sharks along the coast of North America, and with a presumed gestation period of 18 months, this placed mating between October and January, during the period when white sharks are known to be at Guadalupe Island. Tracking data during the time sharks were offshore showed that mature males and females are spatially segregated, except for their concurrent seasonal presence at Guadalupe Island. These discoveries provide important new details about the complete life history of northeastern Pacific white sharks while identifying crucial regions in which young-of-the-year, juveniles and adult females are most vulnerable.
Migration routes and wintering areas of Booted Eagles Aquila pennata breeding in Spain
Ugo Mellone, Javier De La Puente, Pascual López-López, Rubén Limiñana, Ana Bermejo, Vicente Urios
Five Booted Eagles breeding in Spain were tracked by GPS during migration. Autumn routes were generally more eastern than spring routes, showing a typical loop migration. Birds covered on average ca. 200 km/day, and only one individual used a long-term stopover site (for up to 4 weeks). All but one used a single wintering area, located in Sub-Saharan Africa, at 2800–3500 km from their nests. Eagles were forced to stop migration at the Strait of Gibraltar for up to 6 days.
Siverio, M., López-Suárez, P., Siverio, F., Rodríguez, B., Varo-Cruz, N. and López-Jurado, L. F. (2013), Density, nest site characteristics and breeding rates of the osprey (Pandion haliaetus) in the southern limit of its range in the Western Palearctic (Boa Vista, Cape Verde Islands). African Journal of Ecology. doi: 10.1111/aje.12082
Between 2004 and 2007, we studied density, habitat features and breeding parameters of the osprey (Pandion haliaetus) population in Boa Vista Island (Cape Verde). A total of 79 nest structures were identified, 37 of which were occupied for at least 1 year during the study period. The osprey population ranged between 14 and 18 pairs, and the mean density and distance between neighbouring occupied nests were 2.58 pairs per 100 km2 and 3089 m, respectively. Occupied nests were found to be significantly further from the coastline and roads than unoccupied nests, but the distances from villages were similar. The majority (81.1%) of the 37 occupied nests were easily accessible to humans. Mean clutch size was 2.59, average productivity was 0.72 young/active nest, and breeding success was 58.8%. Density in Boa Vista was higher than that in other sedentary island populations in the Western Palearctic, whereas the productivity was the lowest of this region. Clutch size did not vary among Western Palearctic populations, but the differences observed in productivity were likely influenced by local factors that in Boa Vista are attributed to nest depredation by the brown-necked raven (Corvus ruficollis) and to direct human persecution.
O’Keefe, J. M., Loeb, S. C., Gerard, P. D. and Lanham, J. D. (2013), Effects of riparian buffer width on activity and detection of common bats in the southern Appalachian Mountains. Wildlife Society Bulletin. doi: 10.1002/wsb.267
Riparian zones are important to bats, which use them for foraging, roosting, and drinking. To predict effects of timber harvests in riparian areas on bats, more information is needed on the functional width of riparian zones for bats, and how bats respond to forest removal near small perennial streams. From May to August (2004–2007), we studied bat presence and activity in 1 unharvested site and 3 harvested sites with different riparian-buffer sizes (0 m, 10 m, and 30 m) in the southern Appalachian Mountains of the United States. We measured activity at 3 distances from the stream in each site (0 m, stream; 23 m, mid; and 46 m, far), classified bat calls by phonic group, and tested the effect of harvest on overall activity, detection, and naïve occupancy rates for 4 phonic groups. Pre-harvest activity was higher at the far versus stream or mid positions. Position, harvest, and interactions affected post-harvest change in activity in the treatment sites. Pre- and post-harvest activity was similar at all positions in the 30-m site. Activity increased significantly in the 0-m and 10-m sites, likely due to the presence of edge after harvest. Detection probabilities were higher post-harvest for larger bats and occupancy of 0-m and 10-m sites was higher post-harvest for all phonic groups except Myotis. Post-harvest responses suggest that the functional width of riparian zones in our study area is ≥10 m. This study is the first to test the effects of harvesting on use of riparian forests by bats; further long-term landscape-scale studies are needed.
Tomasz Kakareko, Jarosław Kobak, Joanna Grabowska, Łukasz Jermacz, Mirosław Przybylski, Małgorzata Poznańska, Dariusz Pietraszewski, Gordon H. Copp
Competitive interactions for food resources between invasive racer goby Babka gymnotrachelus and native European bullhead Cottus gobio
Biological Invasions, April 2013
Racer goby is one of several Ponto–Caspian gobiids spreading throughout European rivers and concurrent with recent declines in threatened populations of a native species of similar biology, the European bullhead. Although suggestive of competitive interactions, evidence thereof is scarce, so we examined behavioural interactions between racer goby and bullhead (single specimens of each species together, also pairs of each species) under experimental conditions (shared space with two shelters) to determine whether the invader displaces the native species when food resources are limited. Food (live chironomids) was added to a single feeder at rates below satiation levels twice over 24 h (once in light and once in darkness), with fish behaviour (aggressive interactions: attacks and threatening) and feeding activity (time spent near or inside the feeder) recorded using video cameras and infrared illumination. Racer goby exhibited aggressive behaviour towards bullhead (mean = 2.5 aggressive events h−1), but rarely the inverse (threatening only, mean = 0.05 events h−1), significantly limiting bullhead foraging time (by 62 %) and being faster to reach food in the feeding time in 76 % of cases. Gobies were more aggressive during daylight (77 % of all aggressive events occurring in light), and both species spent more time on feeding activities in darkness (88 and 66 % of all time spent in the feeder by bullheads and gobies, respectively). However, the adverse impact of goby on bullhead was independent of light conditions. Our results suggest that under natural conditions, racer goby are likely to displace bullhead during feeding, with potential consequences for foraging efficiency.
Augusto Silva-Costa, Leandro Bugoni
Feeding ecology of Kelp Gulls (Larus dominicanus) in marine and limnetic environments
Aquatic Ecology, April 2013
The diet of the Kelp Gull (Larus dominicanus) was investigated at the northern limit of its distribution along the South American Atlantic coast. We used two complementary methods, pellet analysis and stable isotope analysis (SIA), to describe and compare Kelp Gull feeding ecology in freshwater and marine environments. The assimilated diet over two different time scales was investigated via SIA of plasma and red blood cells, blood components with different turnover rates. Fish composed the bulk of the diet of Kelp Gulls in both marine (White Croaker Micropogonias furnieri and Banded Croaker Paralonchurus brasiliensis) and limnetic areas (Armoured Catfish Loricariidae and La Plata Croaker Pachyurus bonariensis), despite the importance of benthic prey from the intertidal zone in samples collected from the marine environment (Wedge Clam Donax hanleyanus and the Yellow Clam Mesodesma mactroides). The fish consumed by the gulls were common discards from fisheries in both environments, and marine bivalves were found at a high density at the marine beach. Diet varied between the different time scales analysed. Conventional diet data generally agreed with stable isotope model estimates, emphasising the importance of using complementary approaches in dietary studies.
Frank Drygala, Hinrich Zoller
Spatial use and interaction of the invasive raccoon dog and the native red fox in Central Europe: competition or coexistence?
European Journal of Wildlife Research, April 2013
The main objective was to discover extent of interference and/or exploitative competition between the native red fox (Vulpes vulpes) and the introduced, invasive raccoon dog (Nyctereues proconoides) in the intensively used, agricultural landscape of northeast Germany (Mecklenburg-Western Pomerania) using very high frequency (VHF) radio telemetry. We recorded location data for 12 foxes and 16 raccoon dogs between July 2004 and December 2006. Species had similar average home range sizes estimated in each season (K95). Home ranges of adjacent raccoon dogs and foxes overlapped from 0.5 to 74.5 % with a mean of 26.4 %. We found a significantly different home range overlap index between the species showing that raccoon dog ranges shifted between seasons to a greater extent than red fox ranges. The raccoon dog differed significantly from the red fox in its use of habitat types, preferring dense vegetation cover and avoiding open areas. The red fox displayed less preference for or avoidance of specific habitat types. Moreover, an almost neutral inter-specific interaction index ranging from −0.12 to 0.12 indicates that raccoon dogs and red foxes ignored each other. It is concluded that widespread and available resources and differences in spatial use patterns prevent competition between red foxes and raccoon dogs in the agricultural landscape of northeast Germany.
Maria Danise de Oliveira Alves, Ralf Schwamborn, João Carlos Gomes Borges, Miriam Marmontel, Alexandra Fernandes Costa, Carlos Augusto França Schettini, Maria Elisabeth de Araújo, Aerial survey of manatees, dolphins and sea turtles off northeastern Brazil: Correlations with coastal features and human activities, Biological Conservation, Volume 161, May 2013, Pages 91-100, ISSN 0006-3207, 10.1016/j.biocon.2013.02.015.
The objective of the present study was to analyze the distribution of manatees, dolphins and sea turtles off northeastern Brazil through aerial surveys, relating them to specific habitats and human activities, with emphasis on marine protected areas (MPAs). Surveys were conducted between January and April 2010 at 150m altitude and 140kmh−1, using two independent observers. Strip transects were flown in a zigzag pattern. Transects covered 4026km in more than 27 flight hours. A total of 36 sightings of manatees (Trichechus manatus manatus, 41 individuals), 28 of dolphins (Delphinidae, 78 individuals, including 10 Sotalia guianensis) and 256 of sea turtles (Cheloniidae, 286 individuals) were recorded. Manatees and sea turtles displayed solitary habits, while dolphins were commonly seen in groups. Manatees were positively correlated with sea turtles, probably due to their preference for sheltered shallow habitats with favorable conditions for foraging and resting. Furthermore, manatees showed a positive relationship with mangrove estuaries, and medium-sized coastal cities probably due to the intense urban development in many estuarine areas. Manatees and sea turtles were also positively correlated with boats, showing a severe threat for these species. Density of manatees was significantly higher within MPAs with preserved mangrove estuaries than in non-protected areas, while dolphins and sea turtles were observed in high densities MPAs with coral reefs. The elevated density of these organisms shows the vital importance of protecting and adequately managing unique ecosystems to ensure a sustainable future for the populations of severely threatened species.
N. Lloyd, A. Moehrenschlager, D.H.V. Smith, D. Bender, Food limitation at species range limits: Impacts of food availability on the density and colony expansion of prairie dog populations at their northern periphery, Biological Conservation, Volume 161, May 2013, Pages 110-117, ISSN 0006-3207, 10.1016/j.biocon.2013.03.008.
Understanding limiting factors affecting population growth for imperilled species is crucial for conservation and management. This research investigates whether black–tailed prairie dog (Cynomys ludovicianus) populations are food limited on their northernmost range extent. We measured background vegetation rates and used food supplementation in a ‘before–after–control–impact’ (BACI) design to test whether increased food positively impacted prairie dog population density and colony expansion. Experimental results did not support food limitation. Overall, density increased from 2008 to 2009 but remained relatively similar between control and treatment plots. Correlations between natural, non-supplemented vegetation biomass and prairie dog density suggest that natural food availability in 2008 may have driven population growth into 2009. Natural food availability was highly variable among years and prairie dog densities may be impacted by food scarcity in some years but not others. Colony spatial expansion was greater in the absence of food supplementation, suggesting food scarcity may drive colony expansion. This research has important implications for the conservation and management of prairie dogs and species that depend on them such as reintroduced black–footed ferrets (Mustela nigripes) in Canada and other populations across their range.
Laura S. Farwell, John M. Marzluff, A new bully on the block: Does urbanization promote Bewick’s wren (Thryomanes bewickii) aggressive exclusion of Pacific wrens (Troglodytes pacificus)?, Biological Conservation, Volume 161, May 2013, Pages 128-141, ISSN 0006-3207, 10.1016/j.biocon.2013.03.017.
Human conversion of land cover alters biotic communities and sets the stage for ongoing change as species interact within new environments. We studied the response of a native forest specialist, the Pacific wren (Troglodytes pacificus), to immediate and ongoing environmental changes facilitated by urbanization. We found evidence of a synergistic effect of native land cover loss followed by increased aggressive interactions with a native generalist, the Bewick’s wren (Thryomanes bewickii), resulting in the decline of Pacific wrens in urbanizing environments. Pacific wren relative abundance decreased dramatically during and after development, while Bewick’s wrens increased and persisted at greater abundance post-relative to pre-development. Breeding territories of the two species overlapped minimally, suggesting spatial segregation either by differential resource use or territorial aggression. A comparison of territory characteristics revealed the species generally used different resources, although territory composition was increasingly similar at urbanizing sites where the species co-occurred. Territorial playback experiments confirmed that the two species interact aggressively. Analyses of body size, body condition and reproductive success did not suggest Bewick’s wrens negatively impact fitness of Pacific wrens at sites where they co-occurred. In established subdivisions (>10 years old) Bewick’s wrens appear to limit the abundance of Pacific wrens, however this was not yet the case at sites we studied immediately after development. Although the results of this study are not conclusive, our findings are consistent with the hypothesis that new environmental gradients and communities created by urbanization increase competitive interactions among native species.
Zootaxa 3641 (1): 031–40 (22 Apr. 2013)
Insight into the validity of Leptobrachium guangxiense (Anura: Megophryidae): evidence from mitochondrial DNA sequences and morphological characters
WEICAI CHEN, WEI ZHANG, SHICHU ZHOU, NING LI, YONG HUANG & YUNMING MO
Leptobrachium guangxiense Fei, Mo, Ye and Jiang, 2009 (Anura: Megophryidae), is presently thought to be endemic to Shangsi, Guangxi Province, China. A molecular phylogenetic analysis and morphological data were performed to gain insight into the phylogenetic position of this species. Maximum parsimony, maximum likelihood, and Bayesian inference methods were employed to reconstruct phylogenetic relationship, using 1914 bp of sequences from mtDNA genes of 12S rRNA, tRNAVal and 16S rRNA. Topologies revealed that L. guangxiense and Tam Dao (Vietnam) L. chapaense lineage (3A) formed a monophyletic group with well-supported values. The uncorrected p-distance of ~1.4k bp 16S rRNA datasets between Tam Dao L. chapaense lineage (3A) and L. guangxiense is only 0.1%. Morphologically, L. guangxiense and Tam Dao L. chapaense lineage (3A) shared the same characters, and are distinguishable from “true” L. chapaense from the type locality in Sa Pa, Vietnam. Based on morphological characters and mitochondrial DNA, we suggested that the Tam Dao lineages of L. chapaense are conspecific with L. guangxiense. This represents a range extension for L. guangxiense, and a new country record for Vietnam.
Tina W. Wey, Joseph R. Burger, Luis A. Ebensperger, Loren D. Hayes, Reproductive correlates of social network variation in plurally breeding degus (Octodon degus), Animal Behaviour, Available online 21 April 2013, ISSN 0003-3472, 10.1016/j.anbehav.2013.03.035.
Studying the causes and reproductive consequences of social variation can provide insight into the evolutionary basis of sociality. Individuals are expected to behave adaptively to maximize reproductive success, but reproductive outcomes can also depend on group structure. Degus (Octodon degus) are plurally breeding rodents, in which females allonurse indiscriminately. However, communal rearing does not appear to enhance female reproductive success, and larger group sizes are correlated with decreasing per capita pup production. To further investigate mechanisms underlying these patterns, we asked how differences in sex, season and average group reproductive success are related to degu association networks. We hypothesized that if reproductive differences mirror social relationships, then females (core group members) should show stronger and more stable associations than males, and female association strength should be strongest during lactation. We also hypothesized that, at the group level, social cohesion would increase reproductive output, while social conflict would decrease it. Females did have higher association strength and more preferred partners than males, but only during lactation, when overall female associations increased. Females also had more stable preferred social partnerships between seasons. A measure of social cohesion (average association strength) was not related to per capita pup production of female group members, but potential social conflict (heterogeneity of association strengths) was negatively related to per capita pup production of female group members. Our results highlight temporal and multilevel patterns of social structure that may reflect reproductive costs and benefits to females.
Moore, J.-S. and Fraser, D. J. (2013), Puny males punch above their weight to preserve genetic diversity in a declining Atlantic salmon population. Molecular Ecology, 22: 2364–2365. doi: 10.1111/mec.12222
Many salmonid fish populations have anadromous (i.e. migratory) and nonanadromous individuals co-existing in sympatry. The nonanadromous individuals, frequently males, mature at a much smaller size in freshwater without undergoing marine migrations and often successfully fertilize many eggs laid by anadromous females. Because these small males do not recruit to fisheries, they are often not regarded in high esteem by fishers. In this issue of Molecular Ecology, Johnstone et al. demonstrate that by substantially contributing to reproduction, such males help maintain genetic diversity in a declining population of Atlantic salmon (Salmo salar). Their results show that estimates of effective population size (Ne), obtained by counting the number of anadromous adults returning from sea and correcting for unequal sex ratios, are lower than estimates generated from genetic markers. Many mechanisms are expected to reduce Ne below the adult census population size (N); the opposite pattern of Ne > N observed by Johnstone et al. is difficult to explain unless the reproductive effort of nonanadromous males is accounted for. The results have important implications for the conservation of small populations and highlight the challenges of relating Ne to N in organisms with complex life histories.