Creator: Andre Meyer
Credit: Getty Images/iStockphoto

Climate change affects not just large, cold-adapted animals in the arctic like polar bears, but also the small creatures that live in warmer climates. Numbats (Myrmecobius fasciatus) are small marsupials native to Australia that are greatly affected by the warming temperatures. Numbats are the only marsupials in Australia that are only active during the day when temperatures are at their highest. These adorable squirrel-like animals forage for termites that live in the ground and in rotting logs. Since termites do not provide many calories in their diet, numbats have evolved to conserve body heat that protects them in cooler temperatures. When temperatures exceed 72 degrees, a numbat may spend only about 10 minutes in the sun before overheating, researchers reported in the Journal for Experimental Biology (Cooper and Withers 2024). If temperatures rise above this limit, which often happens with recent rapidly heating global temperatures, a numbat may not have much time to forage during the day at all. Even ducking in the shade during the day is not enough to help keep numbats cool. The research team studying numbat foraging activity, calculated that only 18% of the heat rising a numbat’s internal body temperature, comes from direct sunlight. The high air temperatures and heat trapped in the ground also warm the numbat’s body to its limit. A possible solution that numbat’s may try is limiting their foraging to the early morning or late evening to escape the high temperatures during the day. This may only be viable for a limited amount of time until even these cooler times will become too hot if global temperatures continue to rise, and even before then, this may not be enough time to forage and satisfy the animal’s energy needs. This already endangered animal is struggling with the pressure of predation from cats and foxes is now faced with the threat of climate change like many wildlife species around the world. Further research into how the loss of termite foraging will impact numbat populations is a key next step for the conservation of this species.

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Numbats are built to hold heat, making climate change extra risky for the marsupials

Research Source:

C. E. Cooper and P.C. Withers. Implications of heat exchange for a free-living endangered marsupial determined by non-invasive thermal imaging. Journal of Experimental Biology. Vol. 226, January 7, 2024. doi: 10.1242/jeb.246301.

Photo credits: Katriona McCarthy

A familiar scene unfolds – it’s a picnic in a park. Young children run screaming around a gingham blanket laden with sandwiches and fresh lemonade. The sky is clear, the birds are chirping, and the nearby pond is full of happily quacking ducks. A little boy grabs a slice of bread from the sandwich pile and, encouraged by his mother, begins to feed the ducks. It’s a picturesque scene, and one we’re all familiar with. The practice of feeding wild ducks is popular across continents in western society, and for most, the food of choice is bread (1). But while feeding ducks bread might be fun for humans, for the ducks it spells nutritional disaster. 

Different species of ducks and other waterfowl have varying natural diets but they all share one trait – none include bread. The duck digestive system evolved to eat weeds, insects, and small aquatic animals. Bread and other processed human foods have a completely different nutritional profile from what ducks are used to, leading to some pretty severe consequences when bread makes up a large portion of the diet (2). Researchers in Australia found that when magpies were fed a diet of processed human foods their cholesterol levels shot through the roof, far higher than is normal for them (3). Their body mass also increased, gaining close to 4% more weight in between just two study periods. 

Photo credits: Pierre-Selim

The young boy finishes feeding the ducks and heads back to the picnic blanket, happily chowing down on some chips. This time he is admonished by his mother, told not to fill up on fatty foods. Unbeknownst to the mother a parallel scene had just played out in front of her, but there is no one to warn the ducks. Weight gain and high cholesterol spell trouble at any doctor’s appointment, and it’s no different for birds. High cholesterol can cause fat developments in arteries and veins, slowing blood flow, and weight gain will make daily tasks more difficult (4). Another study, this time conducted on swans, found even more concerning results. Swans who ate a lot of bread were found to have a lower muscle mass than swans on a natural diet, putting them at risk of predation because they can no longer flee as fast and disrupting their ability to integrate into swan society because activities like migration and breeding become much harder (5). The malnutrition issues that result from feeding waterfowl bread seems endless. Another study, also investigating swans, found a connection between humans feeding wildlife and a condition known as ‘angel wing’, when a bird’s wing sticks up at an improper angle, permanently preventing them from flying (6). 

As fun as it is to interact with wildlife and throw some bread to the little duckies, it’s not as harmless or innocuous as it seems. Much like our young boy at his picnic, ducks will fill up on whatever tastes best, even if that’s not what is really best. It’s up to us, as parents and stewards of the earth, to take responsibility and stop offering unhealthy food to someone we know can’t say no. 

Photo credits: Dave Stokes

1. Chapman, R., Jones, D. (2010). Foraging by native and domestic ducks in urban lakes: behavioural implications of all that bread. Corella. 35(4): 101-106. https://absa.asn.au/corella_documents/foraging-by-native-and-domestic-ducks-in-urban-lakes-behavioural-implications-of-all-that-bread/ 
2. Burt, S. A., Vos, C. J., Buijs, J. A., & Corbee, R. J. (2020). Nutritional implications of feeding free‐living birds in public urban areas. Journal of Animal Physiology and Animal Nutrition, 105(2), 385–393. https://doi.org/10.1111/jpn.13441 
3. ISHIGAME, G., BAXTER, G. S., & LISLE, A. T. (2006). Effects of artificial foods on the blood chemistry of the Australian magpie. Austral Ecology, 31(2), 199–207. https://doi.org/10.1111/j.1442-9993.2006.01580.x 
4. High cholesterol – Symptoms and causes. (2023, January 11). Mayo Clinic. https://www.mayoclinic.org/diseases-conditions/high-blood-cholesterol/symptoms-causes/syc-20350800#:~:text=With%20high%20cholesterol%2C%20you%20can,a%20heart%20attack%20or%20stroke 
5. Sears, J. (1989). Feeding activity and body condition of Mute Swans Cygnus olor in rural and urban areas of a lowland river system. Wildfowl Journal, 40, 88-98. https://wildfowl.wwt.org.uk/index.php/wildfowl/article/view/812/812n 
6. Mustafa ARICAN, Kurtuluş PARLAK, Mustafa YALÇIN. (2019). Angel Wings Syndrome in Swans (Cygnus cygnus and Cygnus atratus). Kafkas Univ Vet Fak Derg, 25 (6): 873-877. 10.9775/kvfd.2019.21995 

Epaulette sharks (Hemiscyllium ocellatum) inhabit the Great Barrier Reef and are known to be tolerant of extreme conditions (Wheeler et al 2021). Female sharks lay eggs in the coral of the reef and leave them unprotected, where they hatch after approximately four months (Gamillo 2021).

Figure 1. Epaulette shark (Hemiscyllium ocellatum) (Image courtesy of Smithsonian Magazine)

Epaulette sharks are native to the Great Barrier Reef. They hunt in isolated tidal pools and lay their eggs in the coral of the reef. These sharks are known to be able to survive extreme conditions which makes them a good study species when looking at the potential effects of climate change.

Oceans “soak up” heat trapped in the atmosphere. When excess energy is added to the climate through things like burning fossil fuels, the ocean will absorb some of that energy (WHOI). Water can hold more heat than land, so it warms more slowly; even so, since the Industrial Revolution (around the 1860s) the ocean has warmed approximately 1.5 degrees Celsius (Deng 2024). These warming waters cause sea level rise, weather changes, coral bleaching, altered ecosystems, etc.

Warming waters raise concerns for species like sharks because they are ectotherms meaning water temperatures affect the body’s biological and physiological processes (how the body works: development rates, metabolism) (Wheeler et al 2021). Many shark species are threatened because they have slow generation times and low reproductive output; meaning they do not frequently have babies and it takes a long time for those babies to grow up. For species like Epaulette sharks that are known to be more tolerant of extreme conditions, their embryos are still at risk because they are unprotected (Wheeler et al 2021).

A study was done where scientists reared 27 epaulette sharks at different temperatures (27,29, and 31 degrees Celsius). These temperatures were chosen based on their current average habitat temperature and predicted future ocean temperatures (Wheeler et al 2021). After birth, they tracked the growth, development, and metabolic costs of the sharks. The results of the study were that sharks reared at higher temperatures consumed their yolk faster, hatched earlier, weighed less, and exhibited reduced metabolic performance (Wheeler et al 2021). These results are concerning because sharks born at higher temperatures were smaller and weaker, putting them at risk for survival. The reduction in metabolic performance at increased temperatures is especially concerning because it means these sharks will be weaker, lose energy faster, and could have a harder time hunting for food successfully (Wheeler et al 2021).

Considering this is a known tolerant species, and they are negatively impacted by increased temperatures, that raises concerns for species that are not as tolerant. If species that were thought to be able to handle extremes actually can’t, then what does that mean for everything else? More research needs to be done on how increased temperatures could affect not only this species but other marine animals. More research also needs to be done on potential alternative solutions for this species because moving habitats may not be an option for them since they use the coral reef environment for hunting and reproduction. If the effects of ocean warming become too extreme, this species may need to find a way to move to colder waters or risk dying off.

References

Deng W (2024) Ocean warming and warning. Nature Climate Change, https://doi.org/10.1038/s41558-023-01921-z

Gamillo E (2021) Ocean warming threatens baby sharks in the Great Barrier Reef. https://www.smithsonianmag.com/smart-news/ocean-warming-threatens-baby-sharks-great-barrier-reef-180976788/ (date last accessed 2 April 2024).

Wheeler C, Rummer J, Bailey B, Lockwood J, Vance S, Mandelman J (2021) Future thermal regimes for epaulette sharks (Hemiscyllium ocellatum): growth and metabolic performance cease to be optimal. Scientific Reports, https://doi.org/10.1038/s41598-020-79953-0

WHOI, Ocean Warming. https://www.whoi.edu/know-your-ocean/ocean-topics/climate-weather/ocean-warming/ (date last accessed 3 April 2024).

We are seeing many species struggle with rising global temperatures amidst climate change. However, multiple studies have shown that the rainbow trout (Oncorhynchus mykiss) has an impressive ability to acclimate to these changes. The rainbow trout is a cool-water species native to the northern Pacific and its tributaries (National Park Service 2015).

Photo courtesy of the Ohio Department of Natural Resources.

A study by Adams et al. (2022) used a population of 3,000 hatchery trout to assess their thermal acclimation potential. The fish were separated into tanks and tested at a range of temperatures from 15-25 degrees Celsius. Despite being a cool-water species that prefers waters below 20 degrees Celsius, the results found that the fish were able to consistently acclimate to temperatures above 20 degrees.

Li et al. (2024) conducted a similar study by testing the mitochondria and livers of rainbow trout after acclimating them to warmer temperatures. They found that acclimation can greatly reduce liver damage and improve mitochondrial function when the trout are exposed to increased temperatures.

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Despite only being native to the Pacific, rainbow trout are stocked throughout the US and other countries as a valuable sport fish. Their ability to acclimate to a warming climate will be a useful tool for managing fish species in the future.

Sources:

Adams OA, Zhang Y, Gilbert MH, Lawrence CS, Snow M, Farrell AP (2022) An unusually high upper thermal acclimation potential for rainbow trout. Conservation Physiology 10(1).

Li H, Yu H, Zhang X, Huang W, Zhang C, Wang C, Gao Q, Dong S (2024) Temperature acclimation improves high temperature tolerance of rainbow trout (Oncorhynchus mykiss) by improving mitochondrial quality and inhibiting apoptosis in liver. Science of Total Environment 912.

Rainbow Trout. National Park Service. https://www.nps.gov/shen/learn/nature/rainbow-trout.htm

Rainbow Trout. Ohio Department of Natural Resources. https://ohiodnr.gov/discover-and-learn/animals/fish/rainbow-trout

African Lion (Getty Images)

The African lion (Panthera Leo), a species that has shown remarkable resilience, has been listed as a threatened species in the Federal Register since 2014 due to poaching, a decline in prey species, and habitat loss and fragmentation(Federal Register, 2015). Most African lion populations, despite these challenges, live in GPAs (government protection areas), which serve as crucial sanctuaries protecting species from poaching and human interactions(Schutte et al., 2013). However, the encroachment of human development has led to a significant reduction in the land African lions freely roamed, nearly 8% in the last century (Sargent et al., 2021). This encroachment has also increased human and lion interactions, often resulting in human or lion injury or fatality. Lions have adapted to this changing landscape by venturing closer to human populations, drawn by the proximity of communities to GPAs and the abundance of prey in the form of livestock(Gebresenbet et al., 2018).

Interactions between Lions and humans are usually negative and have influenced a behavioral shift for both parties. Lions have been shown to become more tolerant and comfortable living near urban communities(Schutte et al., 2013). Studies have shown that some wild lions release nearly the same amount of glucocorticoids as lions that live in zoos when confronted by humans(Sargent et al., 2021). This change in the fight or flight response of human interaction could mean trouble for future lion generations, as the typical way of dealing with a socialized lion is by shooting the animal (Federal Register, 2015). A behavioral shift in humans is observed in studies taken from communities that live near lions, asking members their opinions about lions. 63% of respondents say they would not increase lion populations and instead push Lions’ native habitat farther away from human civilization(Schutte et al., 2013). This solution to Lion interactions in communities could drive lions into endangered territory as land would be even more downsized. Local governments and protection agencies have begun tackling this growing issue by urging community residents not to interact with Lions or native species and instead avoid all possible interactions (Gebresenbet et al., 2018). Protecting livestock to minimize predation amongst lions is also incentivized to reduce the urge for Lions to hunt in human-populated areas (Gebresenbet et al., 2018). Much is to be done to protect the sanctity of African lions and further population density loss, which lies in the hands of community members, individuals in legislative power, and law enforcement (Sargent et al., 2021).

References:

Branch of Foreign Species. (2015). Endangered and Threatened Wildlife and Plants; Listing Two Lion Subspecies. Federal Register . https://www.federalregister.gov/documents/2015/12/23/2015-31958/endangered-and-threatened-wildlife-and-plants-listing-two-lion-subspecies#:~:text=On%20October%2029%2C%202014%20(79,threatened%20species%20under%20the%20Act.

Schuette, P., Creel, S., & Christianson, D. (2013). Coexistence of African Lions, livestock, and people in a landscape with variable human land use and seasonal movements. Biological Conservation, 157, 148–154. https://doi.org/10.1016/j.biocon.2012.09.011

Sargent, R., Deere, N. J., McGowan, P. J. K., Bunnefeld, N., & Pfeifer, M. (2021). Room to roam for african lions panthera leo: A review of the key drivers of Lion Habitat use and implications for conservation. Mammal Review, 52(1), 39–51. https://doi.org/10.1111/mam.12262

Gebresenbet, F., Bauer, H., Vadjunec, J. M., & Papeş, M. (2018). Beyond the numbers: Human attitudes and conflict with lions (Panthera leo) in and around Gambella National Park, Ethiopia. PLOS ONE, 13(9). https://doi.org/10.1371/journal.pone.0204320

Large volumes of pesticides are used across the globe in both agricultural and domestic settings. Among the many registered and sold pesticides, atrazine is a leading product. Atrazine is an herbicide formulated to manage annual grasses and broadleaf weeds. It is used most extensively on agricultural crops including field corn, sweet corn, and sugarcane (Graymore et al., 2001). In the United states alone, over 80 million pounds of atrazine are applied on a yearly basis (Hayes et al.2010). Further, it is widely recognized as the primary pesticide contaminant in both ground and surface water, where it adversely affects aquatic organisms (Hayes et al., 2010).

Figure 1: Atrazine on an agricultural field https://www.shutterstock.com/image-photo/atrazine-herbicide-used-on-corn-sorghum-2297713451

Atrazine is of great ecological concern because of its ability to act as a potent endocrine disruptor at low concentrations. It has been found to be especially potent to amphibians at levels as minimal as 0.1 ppb (Hayes et al., 2010). Atrazine acts as an endocrine disruptor in adult frogs by depleting androgens, which are hormones that contribute to growth and reproduction (Hayes et al., 2006).

Hayes et al. (2010) studied the long-term effects of atrazine on African clawed frogs (Xenopus laevis) by exposing them to 2.5 ppb of atrazine over a 3 year time period and by measuring the sex ratios, testosterone levels, sexual dimorphism, reproductive behaviors, and fertility that resulted. They found that 10 percent of the genetically male frogs in their study developed into females that were able to produce viable eggs and mate with other males. Furthermore, they found that atrazine exposure led to suppressed levels of testosterone, reduced spermatogenesis and fertility, and smaller breeding gland size (Hayes et al., 2010). The importance of these findings is immense, as the severe reproductive impacts of atrazine may pose a significant threat to the survival of frog populations in the wild.

Figure 2: Feminization of male gonads (Hayes et al., 2011)

References:

Graymore M, Stagnitti F, Allinson G (2001) Impacts of atrazine in aquatic ecosystems. Environment International 26(7):483-495. Doi: 10.1016/S0160-4120(01)00031-9. 

Hayes TB, Anderson LL, Beasley VR, de Solla SR, Iguchi T, Ingraham H, Kestemont P, Kniewald J, Kniewald Z, Langlois VS, Luque EH, McCoy KA, Munoz-de-Toro M, Oka T, Oliveira CA, Orton F, Ruby S, Suzawa M, Tavera-Mendoza LE, Trudeau VL, Willingham E (2011) Demasculinization and feminization of male gonads by atrazine: consistent effects across vertebrate classes. The Journal of Steroid Biochemistry and Molecular Biology 127(1): 64-73. Doi: 10.1016/j.jsbmb.2011.03.015.

Hayes TB, Khoury V, Narayan A, Nazir M, Park A, Brown T, Adame L, Chan E, Buchholz D, Stueve T, Gallipeau S (2010) Atrazine induces complete feminization and chemical castration in male African clawed frogs (Xenopus laevis). Proceedings of the National Academy of Sciences

Hayes TB, Stuart AA, Mendoza M, Collins A, Noriega N, Vonk A, Johnston G, Liu R, Kpodzo D (2006) Characterization of Atrazine-induced gonadal malformations in African clawed frogs (Xenopus laevis) and comparisons with effects of an androgen antagonist (Cyproterone Acetate) and exogenous estrogen (17B-estradiol): support for the demasculinization/feminization hypothesis. Environmental Health Perspective 114(1): 134-141. Doi: 10.1289/ehp.8067.

Photo courtesy of Eric Kilby https://openverse.org/image/90cffaeb-e1b5-4f60-80a5-a8ea89c37c2e?q=bat%20eating%20fruit

Bats play a critical role in many ecosystems around the world. They have incredibly diverse eating habits that allow them to occupy different habitats and provide services that are vital to the health and balance of entire ecosystems. For example, fruit-eating bats disperse the seeds in their waste as they fly, nectar-eating bats pollinate plants and insect-eating bats contribute to insect control (Trust BC, 2024). They help pollinate our favorite fruits and they eat the insects that feed on us or our crops. Unfortunately, this relationship isn’t reciprocated. We as a species disrupt these ecosystem services by using pesticides that harm bats (Oliveira et al., 2020).

Pesticides are effective against their target species and help protect crops and livestock from pests (Oliveira et al., 2020). However, when pesticides are applied, they are dispersed through the air and water and they travel to regions that are far from the target site. They then come in contact with non-targeted species. For example, Dichlorodiphenyltrichloroethane (DDT) residues have previously been found in soil, surface water and air and in the tissues of fish, mammals and birds (Oliveira et al., 2020). Pesticide exposure can harm entire populations. The most well-known example is of eagles and their eggs. Eagles exposed to DDT produced eggs with thin shells which halted development of the chicks (US EPA, 2024). This caused population declines in eagles that landed them on the endangered species list.

Bats are exposed to pesticides through a number of mechanisms including contamination of food and water or through skin contact (Oliveira et al., 2020). Exposure to pesticides is mostly dependent on the bat’s feeding habits. Insect-eating bats are at highest risk because they eat agricultural pests that may be contaminated with pesticides. Fruit bats are the second highest at risk to exposure because they forage amongst plants applied with pesticides (Oliveira et al., 2020).

There are several classes of pesticides and their effects on bats differ. Organochlorine pesticides increase the metabolic rate of bats which reduce energy reserves (Oliveira et al., 2020). Reduced energy reserves mean that less energy is dedicated to important processes such as reproduction. This can cause bats to spend more time and energy foraging and puts them at higher risk of predation as well.

Neonicotinoids are another class of pesticides that harm bats. Imidacloprid, a neonicotinoid, interferes with the spatial memory of bats, affecting their echolocation (Hsiao et al., 2016). Chlorpyrifos, belonging to the organophosphate class of pesticides, impairs flight and movement of big brown bats and causes tremors (Eidels et al., 2016). Several organochlorine and pyrethroid insecticides are endocrine disruptors that can affect the reproductive success of bats (Oliveira et al., 2020). For example, fruit-eating bats exposed to a fungivore developed anatomical changes in their testes and epididymis, disrupting their normal reproductive function (Machado-Neves et al., 2018). 

Bats play important roles in the health and balance of their ecosystems. If we lose bats that contribute the most ecosystem services, many organisms that depend on these services for survival will be impacted, including us. Our food production would decrease and we may be exposed to more mosquito-borne diseases. We must advocate for all bat species and do our part to protect them.

References

Eidels RR, Sparks DW, Whitaker JO, Sprague CA (2016) Sub-lethal Effects of Chlorpyrifos on Big Brown Bats (Eptesicus fuscus). Arch Environ Contam Toxicol 71: 322–335.

Hsiao C-J, Lin C-L, Lin T-Y, Wang S-E, Wu C-H (2016) Imidacloprid toxicity impairs spatial memory of echolocation bats through neural apoptosis in hippocampal CA1 and medial entorhinal cortex areas. NeuroReport 27: 462.

Machado-Neves M, Neto MJO, Miranda DC, Souza ACF, Castro MM, Sertorio MN, Carvalho TF, Matta SLP, Freitas MB (2018) Dietary Exposure to Tebuconazole Affects Testicular and Epididymal Histomorphometry in Frugivorous Bats. Bull Environ Contam Toxicol 101: 197–204.

Oliveira JM, Destro ALF, Freitas MB, Oliveira LL (2020) How do pesticides affect bats? – A brief review of recent publications. Braz J Biol 81: 499–507.

Trust BC (2024) Bats as pollinators – Why bats matter. Bat Conservation Trust. https://www.bats.org.uk/about-bats/why-bats-matter/bats-as-pollinators (last accessed 3 April 2024).

US EPA O (2016) The Case of DDT: Revisiting the Impairment. https://www.epa.gov/caddis/case-ddt-revisiting-impairment (last accessed 3 April 2024).