Turning an ecosystem that has been ruined by humans back into a thriving natural world is a long, difficult task, but it is possible. One method for making it easier is re-introducing species that we’ve wiped out. Often the reintroduction of the functions that these species perform helps restore many other species, and helps the ecosystem returns to a more ‘natural’ state.
But what happens when a really key species has gone extinct? One way of solving this conundrum is introducing a similar species that performs the same function. This sounds like a good workaround, but introducing a non-native species might have unexpected ecological repercussions.
This week’s researchers were based on Round Island, in Mauritius, where two species of giant tortoise (the saddle-backed and the domed Mauritius giant tortoise) had gone extinct. A third species, the Aldabra giant tortoise, was introduced in 2007. The main point of concern on the island is that the tortoise diet may overlap with that of a vulnerable species, the Telfair’s skink. This week’s team wanted to find out whether the tortoise was helping or hindering the island.
When an animal is facing a lack of prey, or the weather is making it too difficult for them to keep on keeping on, they might choose to enter a state known as torpor. This occurs when the animal lowers its metabolic rate drastically, sometimes to less that 1% of its normal rate. It’s not a perfect solution though, as the costs of torpor include sleep deprivation and memory loss. Nevertheless, it’s a go-to for many small mammals, since they’re warmed up much more quickly than larger ones, and can snap out of torpor when they need to.
It might sound like this is cold-weather behaviour, but it can also occur in summer. Especially if you’re a nocturnal mammal living in part of the world where nights can be very short, or even non-existent, like Scandinavia. Long days means reduced hunting times, so using torpor might be necessary to get through summers as well as winters! This week’s researchers wanted to better understand how small bats survive in northern Norway by looking at how and when they awake from torpor.
With increasingly clear effects of global climate change, everyone’s thinking about how we will handle extreme temperatures and weather events as they become more common. Less obvious is the fact that the changing climate is also rearranging global food webs, with many species readjusting in the fact of a new range of temperatures. This might not sound fantastic (and let’s face it, it’s not), but this changing climate may be able to teach us something about how species adapt to higher or lower temperatures.
Temperature plays a key role in determining whether an invasive species can take up residence in a new region. We know that low temperatures can be particularly limiting to newly-invasive species, especially insects and spiders. Yet few studies look at how lower temperature in a new environment can affect the survival, development, and behavior of new invaders.
We tested whether invasive widow spiders from a warm climate (Australia) adapted over generations to the lower temperatures of their invaded habitat in Japan. The move to Japan should require adapting to lower temperatures, but it might not, for a few reasons. Spiders from both locations may be equally good at coping with cooler or warmer temperatures, or, since urban areas are typically warmer than natural habitats, organisms that move between urban habitats might avoid facing the low temperature constraints.
Did You Know: Cities as Heat Islands
It’s hot in cities! One reason for this is the urban heat island effect, where urban areas are several degrees hotter than surrounding natural areas because of all of the heat-absorbing surfaces like roads and buildings. More than half of the human population lives in cities, and as they heat up, it is especially important to understand how some species adapt and even do better in urban environments. Urbanization and climate change can also increase the spread of invasive species. For example, some urban-adapted invasive species thrive in urban habitats that would otherwise be too cold for them to survive and reproduce in. Understanding how urbanization, climate change, and invasions interact can help us predict changes in biodiversity and species distributions in the future.
What We Did
The Australian redback spider, Latrodectus hasselti, is an invasive species of widow spider, native to Australia. Redback spiders are well-known in Australia for their bite and neurotoxic venom. Redbacks have been transported (likely accidentally along with used cars or produce) to Japan, New Zealand, the Philippines, Papua New Guinea, and India. We compared traits across native and invasive-habitat temperatures in a native population of spiders. The native spiders were collected from Sydney, Australia and the invasive population from Osaka, Japan, where redbacks became established in 1995.
We reared the spiders in the lab for three generations. We first checked for population differences in how spiders responded to extreme temperatures, measuring the lowest and highest temperatures at which spiders were able to maintain normal activity.
Next, we investigated how spiders respond to more moderate temperature differences, such as those in autumn, right before overwintering. When female spiders from each population produced egg sacs, we put the egg sacs for two weeks in either Japan-typical (15 degrees Celsius) or Australia-typical (25 degrees) autumn temperatures, then put all egg sacs at 25 degrees until spiderlings emerged. We predicted that the invasive spiders from Japan would be better adapted to low temperatures than the native Australian population, as they’re used to colder temperatures. We also measured hatching success, development time, and body size.
Once the spiderlings were juveniles, we measured behavioural traits that may be important for survival in nature: boldness – how quickly a spider resumed movement after a simulated predator threat (a puff of air), and exploration – building a web in a new environment.
What We Found
At extreme high temperatures, spiders from each population were similarly tolerant, with females able to move at temperatures of up to 55 degrees Celsius! Surprisingly, males from the invasive population from Japan were less tolerant of extreme low temperatures, suggesting that they may not overwinter successfully in colder regions. Egg sacs from the Japanese population hatched equally well at low and high temperatures, but egg sacs from the Australian population failed to hatch more often at low temperatures. Native spiders also took longer to emerge from the egg sacs than invasive spiders at low temperatures, which could expose egg sacs to more predation risk.
The Japanese population was bolder and more exploratory at low temperatures, but less bold and less exploratory at high temperatures, whereas the native population was similarly bold and exploratory at both temperatures.
Spiders from Japan, which live in cooler habitats, developed at both low and high temperatures, compared to a native population, which hatched less and developed more slowly when exposed to low temperatures. This study only tested one invasive and one native population, and it would be worthwhile to compare multiple invasive populations from both cooler and warmer habitats, as well as multiple native populations across Australia.
Although the invasive habitat in Japan is more extreme in temperature, spiders also live in more urbanized habitats compared to the native population. Urban habitats are hotter, and we would like to measure what conditions the animals are directly experiencing in the urban and natural habitats, to find out if spiders are able to colonize cooler climates because they thrive in urban heat islands habitats.
Some organisms may be better equipped to deal with changes we are facing with urbanization, habitat fragmentation, and climate change. In the case of Australian redback spiders, within twenty years, we found that an invasive population changed significantly in traits related to thermal performance, which may give them an advantage as temperatures change worldwide.
Behavioral traits are studied less frequently; finding increased variability in an invasive population may provide a clue to how the species can thrive in different environments. Understanding how organisms can establish and spread in environments different from their native ranges can help us predict which species will survive in our increasingly urbanized, changing world.
Dr. MonicaMowery is a Zuckerman STEM postdoctoral fellow in the labs of Yael Lubin and Michal Segoli at Ben-Gurion University of the Negev. She received a B.S. in biology and community health at Tufts University, working on butterfly visual signals and behaviour in Sara Lewis’ lab. Her PhD was conducted in the labs of Maydianne Andrade and Andrew Mason at the University of Toronto Scarborough, where she studied invasion success in widow spiders.You can read more about Monica’s work at her website.
Wind turbines are a constant source of controversy. The planet needs more renewable energy, yet wind turbines represent a threat to many bird populations. There have been a plethora of studies just in the last two years focussing on the impact of the turbines on birds. Yet furrier fliers often get overlooked, and it should come as no surprise that wind turbines can be a large source of mortality for bats as well.
Previously wind turbines were usually built out at sea, or in open, cleared land. Yet there has been a move over the last decade to building more wind turbines in forested areas. Moving further into forests could represent a larger threat for bats, so do they show any behaviour that could help them avoid wind turbines? That’s what today’s researchers wanted to find out.
This week has seen Europe hit by heatwaves of an intensity that would have seemed more at home in the USA’s dust bowl or Australia’s Great Red Centre. Fires have raged across Spain and France, people have been evacuated from and lost their homes, and thousands have died as temperatures seared great swathes of the continent.
While some have sneered at the UK cowering in the face of such heat, there’s no doubting that 40 degrees is pretty scorching, especially in a country where the infrastructure just isn’t built to take it. The full ramifications of these heatwaves are yet to be seen, but the loss of life, and financial costs rising from damage to property and infrastructure, plus the health issues caused by ongoing drought and heatstroke, are only likely to rise as the week goes on.
Now that we’ve covered the depressing stuff that’s happening currently, let’s focus on the future. Is this the new norm?
As the planet warms thanks to climate change, the massive bodies of water that are our oceans grow hotter. Since they’re larger, and much poorer conductors of heat, they don’t tend to vary in temperature as much as the land does, which means many species will have to get used to longer, warmer periods.
If species can adapt to hotter temperatures through thermal acclimation, ecosystems may not be too harshly affected. However if they’re unable to adapt, marine ecosystems may undergo rapid changes as they lose native species. Today’s researchers looked at a key study species – the zebrafish – in order to figure out how well fish can respond to increasing temperatures.
As I write this, I can hear invasive myna birds chirping in the trees outside, and see yellow pollen from the invasive Acacia trees floating through the air. What makes these species able to thrive far away from their native habitat? Despite the knowledge of how harmful invasive species can be, humans continue to transport species to new environments, both intentionally and unintentionally. Yet even with the explosive growth of both invasive species and invasion ecologists, we still don’t know a lot about which traits make the most successful invaders that can thrive and spread to new places.
One way to investigate this is to compare invasive populations that have just arrived at a new place with populations that have been in an area for a long time. To better understand invasive species, we need to figure out how traits shift in invasive populations, as some individuals survive transport, establish, and spread to new habitats, expanding their range. When this happens, traits can change, or shift, as the species adapt to the new environment. Such traits, such as body size, number of offspring, and dispersal ability, may be particularly important during range expansion. This study is an investigation into how traits of invasive spiders shift on a broad geographic scale on two continents.
Achieving international biodiversity targets: learning from local norms, values and actions regarding migratory waterfowl management in Kazakhstan (2022) Jones et al., Journal of Applied Ecology, https://doi.org/10.1111/1365-2664.14198
Some species that we consider local treasures have ranges that extend over vaste swathes of the planet, and some of these make use of those entire ranges. This is probably most obvious in bird species. Some of the locals that have been popping up in my neighbourhood as spring kicks off have been spending the winter on the other half of the planet, and have made use of countless other locations on their journeys between the two endpoints.
This makes conservation a headache. Just because a species is beloved and protected at one end of its range doesn’t mean it’s afforded the same luxury at another end. Even if the species is internationally recognised as threatened, that doesn’t mean every location it visits will respect – or even be aware – of this status. That means that to protect migratory species, we need to figure out the most important parts of their ranges, and work with the people who live there to ensure the birds persist. Today’s paper is an investigation into how effective this sort of work could prove in the future.
Trains are one of the most climate-friendly ways to cross long-distances. Whether it’s people heading off on holiday or transporting food, clothing or other goods, it’s a (usually) cheap and low-emissions method of travel.
Yet train-animal collisions can be a massive problem for wildlife. Deer in Europe, bears in North America, and elephants in India are three of the many, many groups of species that suffer mortalities every year when they’re hit by trains. The collisions aren’t exactly friendly to the trains either, with many drivers suffering from trauma and repairs often need to be made (granted, not as bad as being run over).
Understanding more about animal behaviour in the face of a train can help us figure out how to prevent these collisions. Today’s authors enlisted the help of Swedish train drivers in an attempt to understand how animals behave when confronted with an oncoming mass of metal.
Let’s face it, IPCC reports are never a fun read. They’re a damming assessment of our ability to take care of the only planet we’ve got. Piecing through them to find the key takeaways is likewise a tough task, but since the final report (for this round) has now been submitted, I thought I’d reflect on what I’ve learned going through each step of the report over the last year.