Changes In Nutrient Availability Research Articles

Dietary fatty acids modulate oxidative stress response to air pollution but not to infection

Anthropogenic changes to the environment expose wildlife to many pollutants. Among these, tropospheric ozone is of global concern and a highly potent pro-oxidant. In addition, human activities include several other implications for wildlife, e.g., changed food availability and changed distribution of pathogens in cities. These co-occurring habitat changes may interact, thereby modulating the physiological responses and costs related to anthropogenic change. For instance, many food items associated with humans (e.g., food waste and feeders for wild birds) contain relatively more ω6-than ω3-polyunsaturated fatty acids (PUFAs). Metabolites derived from ω6-PUFAs can enhance inflammation and oxidative stress towards a stimulus, whereas the opposite response is linked to ω3-derived metabolites. Hence, we hypothesized that differential intake of ω6-and ω3-PUFAs modulates the oxidative stress state of birds and thereby affects the responses towards pro-oxidants. To test this, we manipulated dietary ω6:ω3 ratios and ozone levels in a full-factorial experiment using captive zebra finches (Taeniopygia guttata). Additionally, we simulated an infection, thereby also triggering the immune system’s adaptive pro-oxidant release (i.e., oxidative burst), by injecting lipopolysaccharide. Under normal air conditions, the ω3-diet birds had a lower antioxidant ratio (GSH/GSSG ratio) compared to the ω6-diet birds. When exposed to ozone, however, the diet effect disappeared. Instead, ozone exposure overall reduced the total concentration of the key antioxidant glutathione (tGSH). Moreover, the birds on the ω6-rich diet had an overall higher antioxidant capacity (OXY) compared to birds fed a ω3-rich diet. Interestingly, only the immune challenge increased oxidative damage, suggesting the oxidative burst of the immune system overrides the other pro-oxidative processes, including diet. Taken together, our results show that ozone, dietary PUFAs, and infection all affect the redox-system, but in different ways, suggesting that the underlying responses are decoupled despite that they all increase pro-oxidant exposure or generation. Despite lack of apparent cumulative effect in the independent biomarkers, the combined single effects could together reduce overall cellular functioning and efficiency over time in wild birds exposed to pathogens, ozone, and anthropogenic food sources.

Estimating growth using an ecophysiological and scope for growth model for the mussel Perna perna grown under suspended culture in Santa Catarina, Brazil

We present a dynamic simulation ecophysiological model for an important aquaculture mussel, Perna perna, grown under suspended culture in Santa Catarina, Brazil. The ecophysiological model was divided in four sectors; driving variables, feeding, energy reserve, and growth. This generated descriptions and explanations of the functions controlling feeding and metabolic responses to changing food availability and seawater temperature. The driving variables sector included time-series of seston variables likely to influence food and energy acquisition in mussels. It included relationships among seston variables to estimate the energy content of phytoplankton, the main component of mussel diet. The feeding sector described mussel suspension-feeding behavior measured using natural seston. Rates of filtration, rejection, ingestion, and absorption were directly related to the quantity and quality of available food. In the energy reserve sector, absorbed matter was transformed to absorbed energy using estimates of energy content of food provided in the driving variables sector. After accounting for the maintenance requirements of the mussels (heat loss and excretion), surplus energy, or the scope for growth, was directed to the growth sector. The growth sector included byssus, organic shell, and soft tissue production based on energy partitioning estimated from monthly measurements of somatic and reproductive tissue and shell growth. The model successfully predicted mussel growth during the study and provided estimates of the response to food acquisition, energy expenditure and allocation to growth. This was the first attempt to model the ecophysiology of this fast growing sub-tropical mussel. Given the capacity of this ecophysiological model to estimate growth of mussels, it has significant economic and environmental value in estimating carrying capacity to support sustainable management of shellfish farming in Brazil.

Hierarchical foraging strategies of migratory short-tailed shearwaters during the non-breeding stage

Foraging specialisations are common in animal populations, because they increase the rate at which individuals acquire food from a known and reliable source. Foraging plasticity, however, may also be important in variable or changing environments. To better understand how seabirds might respond to changing environmental conditions, we assessed how plastic the foraging behaviours of short-tailed shearwaters (Ardenna tenuirostris) were during their non-breeding season. To do this, we tracked 60 birds using global location sensing loggers (GLS) over a single year between 2012 and 2016 with the exception of 8 individuals that were tracked over 2 consecutive years. Birds predominantly foraged in either the Sea of Okhotsk/North Pacific Ocean (Western strategy) or the southeast Bering Sea/North Pacific (Eastern strategy). The eight birds tracked for 2 consecutive years all returned to the same core areas, indicating that these birds were faithful to foraging areas between years, although the time spent there varied, probably in response to local changes in food availability. Overall, 50% of the birds we tracked left their core area towards the end of the non-breeding period, moving into the Chukchi Sea, suggesting that the birds have flexible intra-seasonal foraging strategies whereby they follow prey aggregations. We hypothesise that seasonal declines in chlorophyll a concentrations in their primary core foraging areas coincide with changes in the availability of large-bodied krill, an important food source for short-tailed shearwaters. Decreasing prey abundance likely prompts the movement of birds out of their core foraging areas in search of food elsewhere. This strategy, through which individuals initially return to familiar areas but disperse if food is limited, provides a mechanism that allows the birds to respond to the effects of climate variability.

Lessons on food security from the COVID-19 pandemic in Bermuda.

Compared with other OECD countries, Bermuda ranks third globally in terms of income inequality globally. During the COVID-19 pandemic, anecdotal evidence suggested, significant fluctuations in the food demand and supply. We aimed to examine the impact of the COVID-19 pandemic on food insecurity, with a focus on the availability and affordability of various foods in Bermuda. We utilized a cross-sectional study design to investigate potential drivers of food insecurity within the local population. To gauge the level of household food insecurity we relied on the Bermuda Omnibus survey (N = 400) undertaken by Total Research Associates Ltd via telephone. To assess changes in food availability and affordability we conducted semi-structured interviews with key stakeholders who played pivotal roles in shaping food accessibility availability and affordability of food in Bermuda. These interviews were systematically analysed using the framework method. We performed analyses of food retail and import data to evaluate fluctuations in food prices and their impact on food availability and affordability. We found statistically significant associations between changes in food consumption, household income, and government aid. Food aid beneficiaries ate fewer fruits and vegetables by 50% [95% CI:17%-83%] and less fresh meat and fish by 39% [95 CI:3%-75%] compared with residents who did not receive any aid during the COVID-19 period from March 2020 to March 2021. Although we did not identify statistically significant food price increases feeding programmes played a pivotal role in preventing food insecurity during the pandemic in Bermuda. However, a lack of monitoring regarding the nutritional quality within the programmes, allowed a wide availability of foods high in sugar, salts, and fats, disproportionately affected low-income populations. In conclusion, food availability in Bermuda remained largely unaffected during the pandemic. Nevertheless, the surge in demand for feeding programs underscores underlying food security challenges in Bermuda and warrants further attention.

The impact of poor fetal growth and chronic hyperpalatable diet exposure in adulthood on hippocampal function and feeding patterns in male rats.

Poor fetal growth affects eating behavior and the mesocorticolimbic system; however, its influence on the hippocampus has been less explored. Brain insulin sensitivity has been linked to developmental plasticity in response to fetal adversity and to cognitive performance following high-fat diet intake. We investigated whether poor fetal growth and exposure to chronic hyperpalatable food in adulthood could influence the recognition of environmental and food cues, eating behavior patterns, and hippocampal insulin signaling. At 60 days of life, we assigned male offspring from a prenatal animal model of 50% food restriction (FR) to receive either a high-fat and -sugar (HFS) diet or standard chow (CON) diet. Behavioral tests were conducted at 140 days, then tissues were collected. HFS groups showed a diminished hippocampal pAkt/Akt ratio. FR-CON and FR-HFS groups had higher levels of suppressor of cytokine signaling 3, compared to control groups. FR groups showed increased exploration of a novel hyperpalatable food, independent of their diet, and HFS groups exhibited overall lower entropy (less random, more predictable eating behavior) when the environment changed. Poor fetal growth and chronic HFS diet in adulthood altered hippocampal insulin signaling and eating patterns, diminishing the flexibility associated with eating behavior in response to extrinsic changes in food availability in the environment.

Hydric physiology and ecology of a federally endangered desert lizard.

Animals can respond to extreme climates by behaviourally avoiding it or by physiologically coping with it. We understand behavioural and physiological thermoregulation, but water balance has largely been neglected. Climate change includes both global warming and changes in precipitation regimes, so improving our understanding of organismal water balance is increasingly urgent. We assessed the hydric physiology of US federally endangered blunt-nosed leopard lizards (Gambelia sila) by measuring cutaneous evaporative water loss (CEWL), plasma osmolality and body condition. Measurements were taken throughout their active season, the short period of year when these lizards can be found aboveground. Compared to a more mesic species, G. sila had low CEWL which is potentially desert-adaptive, and high plasma osmolality that could be indicative of dehydration. We hypothesized that throughout the G. sila active season, as their habitat got hotter and drier, G. sila would become more dehydrated and watertight. Instead, CEWL and plasma osmolality showed minimal change for females and non-linear change for males, which we hypothesize is connected to sex-specific reproductive behaviours and changes in food availability. We also measured thermoregulation and microhabitat use, expecting that more dehydrated lizards would have lower body temperature, poorer thermoregulatory accuracy and spend less time aboveground. However, we found no effect of CEWL, plasma osmolality or body condition on these thermal and behavioural metrics. Finally, G. sila spends considerable time belowground in burrows, and burrows may serve not only as essential thermal refugia but also hydric refugia.

Drivers and resilience of methane-derived carbon contribution to chironomid biomass in boreal lakes

General mechanisms underlying the pathways of methane (CH4)-derived carbon in aquatic food webs are often associated with eutrophication-driven anoxia. Yet, the influence of changing nutrient availability on CH4 cycling has been mainly investigated during the increasing phase (i.e. onset of anthropogenic eutrophication), thus leaving unclear whether nutrient reduction can lead to a simple reversion of the observed effects on CH4 cycling. We combined stable isotopes of chironomid remains (δ13CHC) and sedimentary ancient DNA of methanotrophic bacteria (MOB) to unravel the drivers of biogenic CH4 contribution to chironomid biomass in boreal lakes. Using a spatial dataset, our study shows that δ13CHC values were more depleted in hypoxic lakes and were positively associated with methanotrophic bacteria belonging to the γ-proteobacteria class (MOB type I), therefore supporting the view of higher utilization of CH4-derived carbon in anoxic environments. However, this space-for-time substitution approach failed to provide any reliable information on whether lake food webs follow the same pathway in forward and reverse directions. Using downcore reconstruction, our results show that despite a drastic mitigation-induced decrease in nutrient concentrations and strong evidence of biological recovery of algal and chironomid communities, chironomid biomass remained highly subsidized by methanotrophic bacteria throughout the study period. Results therefore suggest that mechanisms underlying the pathways of CH4-derived carbon in aquatic food webs are likely not the same during perturbation and recovery trajectories and that complex feedback mechanisms can stabilize lakes in this CH4-based food web state.

Waterbird community changes in the Wilderness Lakes, South Africa (Part 1 of 3): Herbivores and omnivores

Global and regional degradation and loss of aquatic systems can negatively affect wetland-dependent waterbirds. The Wilderness Lakes Complex in South Africa, which incorporates the Wilderness Ramsar site, supports populations of 68 waterbird species including eight which periodically occur in globally significant (1% population) numbers. The study aimed to document long-term spatial and temporal (including seasonal) patterns of abundance of herbivorous waterbirds in the Wilderness Lakes Complex, and where possible identify potential causes for observed trends. The abundance of waterbirds on these wetlands was determined biannually from 1992 to 2019, with counts conducted from a boat following a standardised route. Historical abundance data from the 1980s was also used to describe long-term abundance changes. Observed seasonality of four herbivorous waterbirds differed from published accounts. Long-term abundance trends indicated a combination of declining, increasing and stable populations which, in several instances, differed from regional (southern African) assessments. Significant long-term decreases have occurred in five herbivorous species in the lakes complex (Common Moorhen Gallinula chloropus, Red-knobbed Coot Fulica cristata, Yellow-billed Duck Anas undulata, Cape Shoveler Anas smithii, Cape Teal Anas capensis), whereas increases have occurred in two species (Spur-winged Goose Plectropterus gambensis, Egyptian Goose Alopochen aegyptiaca). Similar types of change occurred across multiple waterbodies, and in different seasons. The similarity of trends in spatially separated wetlands suggested either high interconnectivity of populations between wetland systems and/or some drivers of change of mobile species being broad scaled and regional, rather than system specific. Local reasons for changes potentially include increasing extent of cultivated fields, a proliferation of emergent macrophytes and loss of open sandbanks, changing food availability, increasing disturbance, and disease.Conservation implications: The fundamental character of the Wilderness Ramsar site has changed, with reduced abundance of several previously abundant herbivorous waterbirds. Drivers of change in species abundances are multifaceted, complex, and frequently poorly understood. Recommended local corrective actions include the management of emergent macrophytes, avian diseases, disturbance, and water quality.

Shrinking body size of European anchovy in the Bay of Biscay.

Decreased body size is often cited as a major response to ocean warming. Available evidence, however, questions the actual emergence of shrinking trends and the prevalence of temperature-driven changes in size over alternative drivers. In marine fish, changes in food availability or fluctuations in abundance, including those due to size-selective fishing, provide compelling mechanisms to explain changes in body size. Here, based on three decades of scientific survey data (1990-2021), we report a decline in the average body size-length and weight-of anchovy, Engraulis encrasicolus L., in the Bay of Biscay. Shrinking was evident in all age classes, from juveniles to adults. Allometric adjustment indicated slightly more pronounced declines in weight than in total length, which is consistent with a change toward a slender body shape. Trends in adult weight were nonlinear, with rates accelerating to an average decline of up to 25% decade-1 during the last two decades. We found a strong association between higher anchovy abundance and reduced juvenile size. The effect of density dependence was less clear later in life, and temperature became the best predictor of declines in adult size. Theoretical analyses based on a strategic model further suggested that observed patterns are consistent with a simultaneous, opposing effect of rising temperatures on accelerating early growth and decreasing adult size as predicted by the temperature-size rule. Macroecological assessment of ecogeographical-Bergmann's and James'-rules in anchovy size suggested that the observed decline largely exceeds intraspecific variation and might be the result of selection. Limitations inherent in the observational nature of the study recommend caution and a continued assessment and exploration of alternative drivers. Additional evidence of a climate-driven regime shift in the region suggests, however, that shrinking anchovy sizes may signal a long-lasting change in the structure and functioning of the Bay of Biscay ecosystem.

Cues of uncommon food habits within dung beetles: Notes from a seasonally dry tropical forest in South America

The assessment of species’ diet and trophic plasticity serve as key elements to understand their adaptations to harsh ecosystems, such as deserts and dry forests. Among dung beetles, coprophagy is the main feeding habit, which may be substituted or complemented by other unusual diets, such as granivory and necrophagy. This study presents new records of dung beetle uncommon diets in Caatinga, the largest Seasonally Dry Tropical Forest in America. We include novel descriptions of the genera Dichotomius Hope, 1838 and Canthidium Erichson, 1847 in using and removing seeds in Caatinga. We also present the first report of dung beetles from Caatinga attracted to dead millipedes, specifically for Coprophanaeus pertyi (Olsufieff, 1924). Also, we found goat hairballs along with the roller beetle Deltochilum verruciferum Felsche, 1911 inside a pitfall trap, suggesting that this species may use animal fur to feed or breed. Finally, we included an updated list on unusual food records of dung beetle species in Caatinga dry forest. Our findings indicate that dung beetles in Caatinga display diverse feeding habits in response to extreme environmental conditions and/or limited resources. We expand the still-scarce knowledge regarding dung beetle feeding ecology outside their interaction with dung or the soft tissues of carrion. Despite our findings, new evidence is essential to reinforce our understanding on trophic plasticity of dung beetles in Caatinga. A better comprehension of resource plasticity by dung beetles will also be a significant input for biodiversity conservation due to the changes in food availability in anthropogenic landscapes.

The impact of food availability on tumorigenesis is evolutionarily conserved

The inability to control cell proliferation results in the formation of tumors in many multicellular lineages. Nonetheless, little is known about the extent of conservation of the biological traits and ecological factors that promote or inhibit tumorigenesis across the metazoan tree. Particularly, changes in food availability have been linked to increased cancer incidence in humans, as an outcome of evolutionary mismatch. Here, we apply evolutionary oncology principles to test whether food availability, regardless of the multicellular lineage considered, has an impact on tumorigenesis. We used two phylogenetically unrelated model systems, the cnidarian Hydra oligactis and the fish Danio rerio, to investigate the impact of resource availability on tumor occurrence and progression. Individuals from healthy and tumor-prone lines were placed on four diets that differed in feeding frequency and quantity. For both models, frequent overfeeding favored tumor emergence, while lean diets appeared more protective. In terms of tumor progression, high food availability promoted it, whereas low resources controlled it, but without having a curative effect. We discuss our results in light of current ideas about the possible conservation of basic processes governing cancer in metazoans (including ancestral life history trade-offs at the cell level) and in the framework of evolutionary medicine.

Effects of temperature and feeding regime on cortisol concentrations in scales of Atlantic salmon post-smolts

Anadromous fish are vulnerable to anthropogenic and environmental stressors including pollution, rising temperatures, and changes in food availability. Knowledge of how fish respond to specific stressors aid our understanding of population declines and inform predictions of how populations will react to future environmental change. There is increasing interest in using cortisol measurements from fish scales to measure chronic stress in fish, however the effects of increased metabolic rate on scale cortisol dynamics must also be considered. This study examines the effect of temperature and feeding conditions on scale cortisol in Atlantic salmon (Salmo salar). Post-smolts were subjected to three different temperatures (6, 10.5 and 15 °C) and four feeding/starvation treatments over a 12-week period. Females held at 6 and 15 °C had significantly higher scale cortisol levels than those held at 10.5 °C, while rearing temperature had no effect on scale cortisol in males. The increase in scale cortisol at 6 °C indicated that temperature related differences were not driven solely by metabolic rate. A two-week starvation period produced an increase in scale cortisol in males and females held at 10.5 °C but not at 6 °C or 15 °C. The study demonstrates that scale cortisol fluctuations can be detected in a low amount (∼10 mg) of Atlantic salmon scales for monitoring of the physiological stress response. Scale cortisol shows potential for monitoring physiological responses during the marine phase in Atlantic salmon. However, the influence of environmental stressors on scale cortisol needs to be better understood, with consideration for sex-specific and interactive effects.

Starvation reduces thermal limits of the widespread copepod Acartia tonsa.

Organismal thermal limits affect a wide range of biogeographical and ecological processes. Copepods are some of the most abundant animals on the planet and play key roles in aquatic habitats. Despite their abundance and ecological importance, there is limited data on the factors that affect copepod thermal limits, impeding our ability to predict how aquatic ecosystems will be affected by anthropogenic climate change. In a warming ocean, one factor that may have particularly important effects on thermal limits is the availability of food. A recently proposed feedback loop known as "metabolic meltdown" suggests that starvation and exposure to high temperatures interact to drastically reduce organismal thermal limits, increasing vulnerability to warming. To investigate one component of this feedback loop, we examined how starvation affects thermal limits (critical thermal maxima: CTmax) of Acartia tonsa, a widespread estuarine copepod. We found that there was no effect of short-duration exposure to starvation (up to 2 days). However, after 3 days, there was a significant decrease in the CTmax of starved copepods relative to the fed controls. Our results provide empirical evidence that extended periods of starvation reduce thermal limits, potentially initiating "metabolic meltdown" in this key species of coastal copepod. This suggests that changes in food availability may increase the vulnerability of copepods to increasing temperatures, amplifying the effects of climate change on coastal systems.

Longitudinal changes in home food availability across the first 3 years of life and associations with family context predictors.

There is limited research tracking changes in home food availability during the first 3 years of life and whether the family context influences these changes. This study examined changes in and predictors of home food availability across the first 3 years of life. This study utilized longitudinal data from the STRONG Kids2 birth cohort from the target child at 6 weeks to 36 months postpartum. Mothers of 468 children were surveyed at 6 weeks, 3, 12, 24, and 36 months postpartum. Home observations were completed by trained research assistants to complete the presence of foods in the home. The primary outcomes were the availability of 10 food groups and scores from the Home Food Inventory (HFI), including dairy (regular fat), dairy (reduced fat), processed meats, other meats and non-dairy protein, savory snacks, vegetables, vegetables (no potatoes), and three obesogenic scores. Repeated measures ANOVA were used to examine changes in the HFI food groups and obesogenic scores over time. Multilevel regressions were conducted to examine whether the presence of an older sibling, entry into childcare, and mother's return to full-time work were associated with the HFI. Significant changes were detected for dairy (regular fat), other meats and non-dairy protein, savory snacks, vegetables, vegetables (no potatoes), and all obesogenic scores across time. A linear trend occurred for most HFI groups, however, the third obesogenic score (without milk and cheese) was highest at 3 months, declined at 12 months, and then slowly increased from 12 to 36 months years. The presence of an older sibling was a consistent predictor of the HFI groups over time. Entry into childcare was only associated with the availability of processed meats. The availability of food types shift as children age and their dietary needs alter. It is important to consider the whole family context such as the presence of older siblings whose dietary needs may differ from younger children. Future efforts are warranted to consider changes in food availability among diverse samples and different family structures.

An agent-based model to quantify energetics, movement and habitat selection of mid-continent mallards in the Mississippi Alluvial Valley

The dynamics of wintering waterfowl populations at the landscape scale are the result of complex interactions of environmental, behavioral and energetic drivers. Agent-based models provide a method to directly link these factors in a spatially explicit framework and allow the emergence of patterns from the aggregation of individual agent actions. We adapted the Spatially-explicit Waterbird Agent-based Model Program (SWAMP), originally developed for waterfowl in central California, to simulate a basin-scale population of mallards (A. platyrhynchos) wintering in the Mississippi Alluvial Valley over a four-month period (November–February). Simulated agents move within the landscape, foraging on areas made available based on a probabilistic inundation status, and converting food resources to endogenous energy. The model uses a high-resolution map of eastern Arkansas waterfowl habitats and incorporates a hierarchical habitat selection system that enables mallards to relocate at increasing scales in response to changing food availability. We validated the performance of modeled mallard body condition and behavioral metrics under a range of environmental conditions against expected outcomes derived from empirical data and found that the simulation produced realistic representations of changes in flight distances, energy expenditure, lipid storage, and foraging habitat use in response to depleting food resources over time. We discuss the model's applicability as a tool to quantify waterfowl response to a range of environmental conditions and to evaluate scenarios of landscape composition and configuration in the context of waterfowl population management.

Weak seasonality in benthic food web structure within an Arctic inflow shelf region

The Arctic Ocean is characterized by pronounced seasonality in the quantity and quality of organic matter exported from the surface ocean. While it is well established that changes in food availability can alter the abundance, biomass and function of benthic organisms, the impact on food web structure is not well studied. We used bulk carbon and nitrogen stable isotope analysis to assess the quantity and quality of sediment organic matter and structure of the benthic food web in four seasons within the Northern Barents Sea (76°N − 82 °C). Despite a highly seasonal vertical flux, we found that the organic carbon and chlorophyll-a content of surface sediments was seasonally stable, suggesting a lack of seasonality in food availability at the seafloor. However, organic biomarkers indicate that the quality of sediment organic matter increased to a maximum in August and December, up to 6 months after the spring bloom. The seasonal stability of food quantity was mirrored in food-web structure (e.g., total isotopic range, number of trophic levels) which did not change significantly across sampling periods. We expected that suspension and deposit feeders would respond more readily to seasonal changes in food quality compared to predators. However, we observed no significant seasonal changes in the trophic levels or isotopic niche areas of benthic functional groups. The centroids of isotopic niches of all benthic functional groups shifted seasonally by <2 ‰ along the δ13C-axis, suggesting minimal shifts in carbon resource use. Because the northern Barents Sea experiences significant changes in seasonal sea ice cover, we expected that stable-isotope ratios of benthic organisms would show an increased consumption of sympagic-derived organic matter through less negative δ13C values in early spring and summer. However, only two taxa (the soft coral Gersemia spp. and bivalves in the family Yoldiidae) showed 13C-enrichment in spring or summer consistent with the assimilation of sympagic-derived organic matter, despite previous evidence suggesting widespread use of this carbon source. Overall, our results show that there is an apparent de-coupling in time between pelagic processes and benthic food-webs in which the accumulation and assimilation of high-quality organic matter occurs for benthos during the fall and early winter months when there is little to no fresh organic matter generated at the surface. This temporal mismatch highlights the importance of considering the timescales over which components of the marine ecosystem respond to short-term environmental changes and the methods employed to assess seasonality.

Abundance of the bottlenose dolphin (Tursiops truncatus) and proposal for a priority area of conservation in the Southern Gulf of Mexico marine ecoregion

Abstract Demographic studies are crucial for assessment of the status of dolphin populations and their relationship with anthropogenic activities as a way to make effective management and conservation decisions. In the Gulf of Mexico, the interaction between bottlenose dolphins (Tursiops truncatus) and anthropogenic activities merits special attention. The objective of this study was therefore to determine the annual abundance and area of preference of the coastal population of T. truncatus (period 2005–2020), and to delimit a priority area for its conservation in the Southern Gulf of Mexico marine ecoregion. Abundance was calculated using the Jolly–Seber model and habitat preference was determined per climatic season (dry, rainy and cold northerly fronts) as a function of environmental variables. The association between anthropogenic activities and dolphin distribution was studied and the priority area delimited using potential distribution models. Off the coasts of Tuxpan and Tamiahua, the results show that the dolphin population numbered 306 individuals (95% CI: 162.97; 607.33) and has remained relatively constant over time. The pattern of dolphin distribution varied between seasons, possibly owing to changes in food availability. However, river mouths and lagoons are of importance to T. truncatus throughout the year. On the other hand, fishing and maritime traffic can potentially affect this species. Finally, this study shows that the delimitation of sites of importance for T. truncatus is a strategic tool with which to help conserve the species and associated coastal ecosystems.

Do changes in body mass alter white blood cell profiles and immune function in Australian cane toads (Rhinella marina)?

Variation in food resources can result in dramatic fluctuations in the body condition of animals dependent on those resources. Decreases in body mass can disrupt patterns of energy allocation and impose stress, thereby altering immune function. In this study, we investigated links between changes in body mass of captive cane toads (Rhinella marina), their circulating white blood cell populations, and their performance in immune assays. Captive toads that lost weight over a three-month period had increased levels of monocytes and heterophils and reduced levels of eosinophils. Basophil and lymphocyte levels were unrelated to changes in mass. Because individuals that lost mass had higher heterophil levels but stable lymphocyte levels, the ratio of these cell types was also higher, partially consistent with a stress response. Phagocytic ability of whole blood was higher in toads that lost mass, owing to increased circulating levels of phagocytic cells. Other measures of immune performance were unrelated to mass change. These results highlight the challenges faced by invasive species as they expand their range into novel environments which may impose substantial seasonal changes in food availability that were not present in the native range. Individuals facing energy restrictions may shift their immune function towards more economical and general avenues of combating pathogens. This article is part of the theme issue 'Amphibian immunity: stress, disease and ecoimmunology'.

Basic human values drive food choice decision-making in different food environments of Kenya and Tanzania

Increased access to a variety of foods in low-and-middle-income countries (LMICs) has led to greater autonomy in food choice decision-making. Autonomy allows individuals to make decisions through negotiation of considerations in ways that are consistent with basic values. The aim of this study was to identify and describe how basic human values drive food choice in two diverse populations with transitioning food environments living in the neighboring East African countries of Kenya and Tanzania. Secondary data analysis was carried out on focus group discussions conducted with men and women in Kenya (n = 28) and Tanzania (n = 28) as part of prior studies on food choice. A priori coding based on Schwartz's theory of basic human values was conducted, followed by a narrative comparative analysis, which included review by original principal investigators. Values of conservation (security, conformity, tradition), openness to change (self-directed thought and action, stimulation, indulgence), self-enhancement (achievement, power, face), and self-transcendence (benevolence-dependability and -caring) were prominent drivers of food choice in both settings. Participants described how values were negotiated and highlighted existing tensions. For example, the value of tradition was cited as important in both settings but changing food contexts (e.g., new foods, diverse neighborhoods) increased prioritization of values like stimulation, indulgence, and self-directed thought and action. The application of a basic values framework was useful for understanding food choice in both settings. A focused understanding of how values drive food choice decision-making in the context of changing food availability in LMICs is essential for the promotion of sustainable healthy diets.

Evidence for density-dependent effects on body composition of a large omnivore in a changing Greater Yellowstone Ecosystem.

Understanding the density-dependent processes that drive population demography in a changing world is critical in ecology, yet measuring performance-density relationships in long-lived mammalian species demands long-term data, limiting scientists' ability to observe such mechanisms. We tested performance-density relationships for an opportunistic omnivore, grizzly bears (Ursus arctos, Linnaeus, 1758) in the Greater Yellowstone Ecosystem, with estimates of body composition (lean body mass and percent body fat) serving as indicators of individual performance over two decades (2000-2020) during which time pronounced environmental changes have occurred. Several high-calorie foods for grizzly bears have mostly declined in recent decades (e.g., whitebark pine [Pinus albicaulis, Engelm, 1863]), while increasing human impacts from recreation, development, and long-term shifts in temperatures and precipitation are altering the ecosystem. We hypothesized that individual lean body mass declines as population density increases (H1), and that this effect would be more pronounced among growing individuals (H2). We also hypothesized that omnivory helps grizzly bears buffer energy intake from changing foods, with body fat levels being independent from population density and environmental changes (H3). Our analyses showed that individual lean body mass was negatively related to population density, particularly among growing-age females, supporting H1 and partially H2. In contrast, population density or sex had little effect on body fat levels and rate of accumulation, indicating that sufficient food resources were available on the landscape to accommodate successful use of shifting food sources, supporting H3. Our results offer important insights into ecological feedback mechanisms driving individual performances within a population undergoing demographic and ecosystem-level changes. However, synergistic effects of continued climate change and increased human impacts could lead to more extreme changes in food availability and affect observed population resilience mechanisms. Our findings underscore the importance of long-term studies in protected areas when investigating complex ecological relationships in an increasingly anthropogenic world.