Angela M. White

Conservation of Avian Diversity in the Sierra Nevada: Moving beyond a Single-Species Management Focus

Background As a result of past practices, many of the dry coniferous forests of the western United States contain dense, even-aged stands with uncharacteristically high levels of litter and downed woody debris. These changes to the forest have received considerable attention as they elevate concerns regarding the outcome of wildland fire. However, attempts to reduce biomass through fuel reduction (i.e., thinning of trees) are often opposed by public interest groups whose objectives include maintaining habitat for species of concern such as the spotted owl, Strix occidentalis, the northern goshawk, Accipiter gentilis, and the Pacific fisher, Martes pennanti. Whether protection of these upper-trophic level species confers adequate conservation of avian forest diversity is unknown. Methodology and Principal Findings We use a multi-species occurrence model to estimate the habitat associations of 47 avian species detected at 742 sampling locations within an 880-km2 area in the Sierra Nevada. Our approach, which accounts for variations in detectability of species, estimates occurrence probabilities of all species in a community by linking species occurrence models into one hierarchical community model, thus improving inferences on all species, especially those that are rare or observed infrequently. We address how the avian community is influenced by covariates related to canopy cover, tree size and shrub cover while accounting for the impacts of abiotic variables known to affect species distributions. Conclusions and Significance Environmental parameters estimated through our approach emphasize the importance of within and between stand-level heterogeneity in meeting biodiversity objectives and suggests that many avian species would increase under more open canopy habitat conditions than those favored by umbrella species of high conservation concern. Our results suggest that a more integrated approach that emphasizes maintaining a diversity of habitats across environmental gradients and minimizing urbanization may have a greater benefit to ecosystem functioning then a single-species management focus.

Communal nesting is unrelated to burrow availability in the common warthog

Warthogs, Phacochoerus africanus, are an unusual ungulate. They are facultative cooperative breeders where females within the same population display both solitary and cooperative reproductive strategies. Warthogs require burrows for sleeping and rearing their young, yet they are unable to dig their own burrows and rely on aardvark excavations. Studies of warthogs have failed to show any reproductive benefits to females participating in communal care and suggest a reproductive cost to cooperation. The ecological constraints hypothesis proposes that environmental factors limit an individual’s ability to successfully disperse and reproduce. In this study we investigated whether limitations in burrow sites can explain cooperative breeding in this species. We checked over 500 burrows for signs of use systematically for 1 year to determine whether burrows were a limiting resource and to investigate burrow use preferences. Our methodology allowed us to determine whether burrows were used by adults with young or by adults without young. We found that burrow availability did not appear to pose an ecological constraint on independent living, as the percentage of burrows used remained relatively low throughout the year. Additionally, the number of burrows in a warthog clan area did not influence the percentage of females breeding cooperatively. Predator avoidance appeared to be the main factor influencing individual burrow selection by warthogs and communal nesting may best be explained as a form of antipredator behaviour.

Is publication rate an equal opportunity metric

Publication quantity is frequently used as a ranking metric for employment, promotion, and grant success, and is considered an unbiased metric for comparing applicants. However, research suggests that women publish fewer papers, such that the measure may not be equitable. We suggest reasons for the disparity, and potential future remedies. Publication quality and impact provide more equitable metrics of research performance and should be stressed above publication quantity.

Differential Investment in Sons and Daughters: Do White Rhinoceros Mothers Favor Sons?

Abstract In species in which one sex experiences greater variation in lifetime reproductive success than the other, the Trivers–Willard hypothesis predicts greater parental investment in offspring of the more variable sex. Support for this hypothesis has been inconsistent and few studies have determined whether differential allocation of resources can be attributed to the parent (as predicted by sex-biased parental investment) or to efforts by offspring to extract resources. We addressed this issue by characterizing maternal investment in wild white rhinoceros (Ceratotherium simum). In a 3-year study, we radiotracked 14 adult females and recorded behavioral activities related to both maternal investment and offspring extraction of maternal resources. Investment in sons appeared to be greater than in daughters: sons suckled significantly longer and more frequently and were weaned significantly later than daughters. Although mothers did not respond differentially to individual nursing solicitations from male versus female offspring, our results suggest that mothers invested more in sons that vocalized at higher rates, but did not alter their investment in daughters in response to call rate. This may indicate that mothers, in part, facilitate access to resources depending on the sex of their offspring. This study provides a useful model for determining whether sex-biased investment is under maternal control or is a consequence of sex differences in the offsprings efforts to extract parental resources.

Grouping patterns in warthogs, Phacochoerus africanus: is communal care of young enough to explain sociality?

Group-living will evolve when individuals increase their lifetime reproductive success by joining with other individuals. In cooperatively breeding societies, individuals living in a group will participate in the communal rearing of young. Several factors can influence the evolutionary trade-offs of grouping and it is often unclear whether cooperative breeding is advantageous or is simply a by-product of selection acting on grouping behaviour. We used sightings of 1318 warthogs in 711 groups to investigate whether the advantages of sociality in the warthog differ depending on an individuals age, sex, reproductive state, or the time of year. Adult males only formed temporary associations with other individuals indicating that participation in a group was not advantageous. In contrast, yearlings were almost inevitably found in groups, regardless of their sex or time of year, suggesting any costs to sociality were outweighed by the benefits. Grouping in adult female warthogs was complex; adult females were more likely to form groups in the presence of juveniles and when juveniles were at their most vulnerable stage indicating that sociality in females could be partially explained by the benefits of communal care of young. However, other factors influenced female cooperation including group composition and the time of year.

Diversity of small mammals in the Sierra Nevada: filtering by natural selection or by anthropogenic activities?

Both historical and contemporary factors may influence the structure and composition of biotas. Small mammal faunas in the Sierra Nevada of California, United States, are strongly dominated by generalist species; however, whereas 1 recent study argues that this is a product of recent anthropogenic influences, another provides a deeper evolutionary explanation based on historic fire frequencies. We summarize these patterns and proposed mechanisms, and we integrate data from 2 other studies—1 in the Sierra Nevada and 1 from an evolutionarily related mountain range in Baja California—to provisionally conclude that evolutionary adaptation, and possibly climatic warming in the Holocene, likely are the primary drivers of this faunal structure. However, we agree with work elsewhere in North America that recent anthropogenic filtering likely has amplified the effects of adaptation and climatic warming; one result of this is that the Sierra Nevada currently supports very limited areas of older (decadent) forests, and species dependent on these habitats may require special attention by resource managers.

Evidence of helping behavior in a free-ranging population of communally breeding warthogs

Cooperative breeding societies are defined by the presence of helpers. Defining helping behavior in cooperatively breeding mammals has been difficult because lactation limits the ability of individuals to provision non-genetic young. As a consequence, “helping” behavior has frequently included predator and conspecific defense and thermoregulation. However, these behaviors are often associated with the benefits of group living and their expression may not warrant a species’ classification as a cooperative breeder (e.g., many ungulates and pinnipeds). In this study, we examine cooperative breeding behavior in the common warthog, Phacochoerus africanus. Warthogs exhibit substantial variation in breeding strategies and females will raise their young alone or in association with other females. The size of warthog groups varies throughout the year and we investigate fission and fusion of individual breeding groups to elucidate the costs and benefits of adopting different reproductive strategies. We found that the cohesion of female groups was related to parturition suggesting that there are benefits to sociality that are related to the production and care of offspring. Additionally, we found that reproductively-aged group members will help other group members by both babysitting and adopting the group’s offspring indicating active selection for cooperation. We did not witness any incidences of yearling group members exhibiting these behaviors indicating differential trade-offs to cooperation possibly related to the helper’s age/experience.

Understanding ecological contexts for active reforestation following wildfires

To forestall loss of ecological values associated with forests, land managers need to consider where and when to prioritize active reforestation following major disturbance events. To aid this decision-making process, we summarize recent research findings pertaining to the Sierra Nevada region of California, USA to identify contexts in which active reforestation or passive recovery may best promote desirable post-fire ecological trajectories. Based on our synthesis, we suggest conceptual frameworks for assessing landscape conditions and determining areas that may be the highest priorities for tree planting to avoid persistent loss of conifer forests. Field studies have shown that some large patches of high severity burn can have relatively low levels of natural regeneration, especially among desired pine species. The accumulation of fuels and competition with shrubs and resprouting hardwoods may hinder the reestablishment of mature conifer trees. However, severe fires could also play a restorative role, by promoting non-conifer forested communities, such as meadows, shrubfields, and open forests with significant hardwood components. Such communities were historically rejuvenated and maintained by fire but have been replaced by conifer forest due in part to fire suppression. Reforestation in such areas may run counter to restoring ecological function and the ecosystem services that are provided by non-conifer communities. Through this framework, managers and stakeholders may better understand the contexts in which planting and passive recovery may better support ecological restoration.

The persistence of Black-backed Woodpeckers following delayed salvage logging in the Sierra Nevada

The Black-backed Woodpecker (Picoides arcticus) is a snag-associated species that colonizes and utilizes patches of burned forests typically within 10 years of fire. Previous research has indicated that salvage logging, the removal of dead and dying trees from burned forests, has a negative effect on nesting densities of Black-backed Woodpeckers. One strategy proposed to ameliorate the impacts of dead tree removal on Black-backed Woodpeckers is to retain patches, or islands, of dense snags within the salvage matrix, but this approach remains largely untested. Following the Angora fire of South Lake Tahoe, CA several snag islands were retained within the larger salvage prescription to conserve habitat for Black-backed Woodpeckers and other snag-associated species. In this observational study, we evaluate whether these snag islands were effective at maintaining Black-backed Woodpecker populations following logging operations that covered 45% of the burned area. We systematically searched the postfire landscape for Black-backed Woodpecker nests for two years before and after salvage operations and compared nesting densities between logged and unlogged areas. Similar to other studies, we found that nest densities at the stand scale declined significantly in areas that were salvage logged, but Black-backed Woodpeckers did nest in both snag islands and in other peripheral unlogged areas, indicating that this approach may help balance habitat for wildlife with management needs at the scale of the fire. In this study, the removal of dead trees, which is usually implemented in the first two years following fire, did not occur until the fourth year, which may have also contributed to the persistence of Black-backed Woodpeckers postlogging.

Publishing: Halt self-citation in impact measures.

We can improve the gender differences in science publishing and research (see V. Lariviere et al. Nature 504, 211–213; 2013) by making measurements of scientific output and impact fairer.