Climate change changes temperature and rainfall patterns, particularly in tropical environments, resulting in consequences for the persistence of wildlife populations. However, the complexities of the effects of changing temperature and rainfall on tropical mammals is not well studied. Together with our colleagues, we studied the demography of the gray mouse lemur in western Madagascar using data collected by the German Primate Center between 1994 and 2020. Climate trends in the lemur’s environment show declining rainfall over the wet season and increasing temperatures in the dry season. These climate trends, we found, led to decreased survival rates as well as increased reproductive rates. The competing demographic trends have prevented population collapse, but have destabilized the population by further speeding up their life cycle which was already one of the fastest among primates. Population projections into the next five decades suggest that when recently observed temperature and rainfall conditions persist, the population size of lemurs may continue to fluctuate, putting the population at increased risk of extinction. Our results show how, even though short-lived mammal species with high reproductive rates are expected to rapidly adapt to changes in their environment, such species can still face threats of extinction from climate change.
The diversity of bird communities in the Swiss Alps is declining more and more, a joint study of the University of Zurich and the Swiss Ornithological Institute has found. An analysis of data from the past two decades has revealed a loss of functional and compositional diversity in Alpine bird communities. This trend is likely connected to rising temperatures and changes in land use.
Ecologists believe that global climate change has had a particularly strong impact on animals and plants living in alpine regions, with expected changes in the distribution, abundance and interaction of species. There is evidence that the habitats of some bird species in Switzerland – such as the tree pipit or the European pied flycatcher – have shifted to higher altitudes in the past two decades. However, the impact of these changes on the composition of bird communities was previously unknown.
Our new study, in collaboration with the Swiss Ornithological Institute (Vogelwarte) has shed new light on this issue. Our study, which is based on two decades’ worth of data collected by volunteer ornithologists, reveals a downward trend. We found that bird communities in the Swiss Alps are undergoing a process of biotic homogenisation; in other words, birds living in this region are becoming less and less diverse.
The crossbill is one of the most functionally distinctive species included in the study. (photo by Valentin Graf)
Functional diversity is important One of the most obvious and simplest ways to measure the diversity of bird communities is by the number of species living in them. However, beyond species richness, the functional diversity of a certain community also provides valuable information. “Different species use resources and interact with the environment in different ways,” says first author, Vicente García-Navas. “Not all species play the same role in an ecosystem. The loss of a given species can be more detrimental than that of several others.” Specialists such as some woodpecker species are particularly important. The holes that they make are used for nesting and as hiding places by other birds and small mammals.
To quantify this functional diversity of bird communities, we compiled information on 100 traits characterising, among other things, the body mass, diet and habitat of each species. This enabled us to examine how the functional diversity of communities changes along the altitudinal gradient and to determine the trend over the past two decades.
High-altitude specialists on the edge Our analyses suggest that the upper forest boundary represents a functional barrier between two distinct groups. One group comprises the lowlands dominated by agriculture landscape and high mountain forests, where species such as the yellowhammer, the common whitethroat and the blackcap live. The other is composed of alpine communities, whose species are adapted to life in the open habitats above the treeline. For example, these species eat fewer caterpillars and build their nests on the ground, such as the rock ptarmigan.
However, the data analyses revealed that functional diversity of Alpine bird communities has decreased over the past few years. “Our study shows that mountain specialists are under increasing risk of becoming misfits,” says co-author Arpat Ozgul. The combined effects of habitat shrinkage, impossibility to find optimal habitats at higher elevations, and upward invasion by generalists are critical factors for these species.
The rise of generalist species This increase in generalist species such as the robin or the European pied flycatcher might also be a reason for the downward trend in the level of variation, or beta diversity, among communities. Our study also found that Alpine bird communities are becoming more and more redundant, with less variation.
“Overall, the study’s results suggest that the joint effect of global warming and land-use changes are boosting an impoverishment of bird communities in the Alps,” says García-Navas. This promotes shrub encroachment and is pushing the treeline upwards, which requires urgent conservation and management actions.
Many animals have evolved life cycles and strategies (patterns of survival and reproduction) in line with predictable seasonal variation in environmental conditions. Short and mild summers produce bursts of vegetation and food, the perfect time to give birth to young. Long, harsh winters when food is scarce have shaped animals to largely depend on fat reserves for energy, and in extreme cases, to hibernate or migrate.
However, climate change is altering these seasonal conditions to which many species are adapted. Temperatures are increasing, winter snowfall is declining, snow is melting earlier, summers are extending, and the frequency of extreme events (e.g., droughts, floods) are on the rise.
Our study, published in the Proceedings of the National Academy of Sciences USA (July 6 2020), found that marmot survival is affected differently by climate change during summer and winter seasons.
In this research, we analysed 40 years of life-history data, collected at the Rocky Mountain Biological Laboratory in Colorado, to understand how yellow-bellied marmots (large burrowing ground squirrels) have responded to climate change during their active summer season and the long winter hibernation.
Dr. Line Cordes, lead author from the School of Ocean Science at Bangor University: “Yellow-bellied marmots are a key indicator species for disentangling the seasonal impacts of climate change as they have a very distinct seasonal life history. They are found in western North America where climate change is more evident than anywhere else on the continent (with exception of the Arctic). Although they are a large rodent (reaching up to 6.5 kg), they are too small to remain active during winter and therefore hibernate for approximately 8 months. Marmots depend on energy stores acquired over the summer, and particular conditions to remain in deep torpor, which lowers energetic costs. Despite hibernation being an effective survival strategy in harsh environments, marmots can still lose up to 40% of their body weight.”
Over the course of four decades (1979-2018), marmot survival generally increased during summer but decreased during winter, and these effects were greatest among pups and one-year-olds.
Climate change at the study site has resulted in warmer winters with less snowfall, and warmer, drier summers which have become significantly longer in duration. Despite the similar seasonal survival trends across pups, one-year-olds and adults, the environmental factors driving these trends differed between the age-classes and seasons. For example, pup summer survival was higher following winters with reduced snowfall, possibly as mothers of these pups were in better condition during pregnancy and while caring for the pups as forage plants appeared sooner due to an earlier snow melt. Winter survival was lower following long, dry summers, most likely as pups were in poorer condition going into hibernation.
Dr. Arpat Ozgul, senior author of the study from the Department of Evolutionary Biology and Environmental Studies at the University of Zurich, said: “The effects of climate change on the fate of a population are determined by the complex interactions of individuals with their biological and physical environment. Our study shows that we need to characterize these complex interactions accurately in order to predict the ultimate effect of climate change on the fate of a population. Critically our findings highlight the care that should be taken in drawing conclusions from annual survival responses to climate change, as this may be a misinterpretation, simplification or even underestimation of the actual more complex responses that can differ dramatically across different times of the year.”
Until now climate change has affected marmot survival positively during the summer months while leaving marmots more vulnerable during winter hibernation. Overall, the net change in survival was negative for pups, positive for yearlings, while there was no change for adults. It is important to note that continued climate change may change the patterns we observed in summer survival, as the persistence of forage plants would ultimately be impacted by progressively warmer and drier summers. Indeed, no marmot population is found in persistently warm and dry habitats.
The fact that climate change may benefit certain species during one season while resulting in unfavorable conditions during another season has potentially wide-ranging consequences across other species occupying temperate to more extreme habitats, such as deserts, mountains and polar regions, where the most rapid changes in climate are being observed. For wildlife living near the poles or near mountain tops, like marmots, there is nowhere to go when environmental conditions become less suitable.
Dr. Line Cordes added: “Social, burrowing, herbivorous mammals, like marmots, play an important role in ecosystem function as they help shape important habitats, and serve as prey for many predators. The loss or decline of these species would likely have wider reaching implications for biodiversity of montane habitats.”
The research was carried out by scientists from Bangor University and the Universities of California Los Angeles, Kansas, Sheffield, Rhode Island, Ottawa, Florida, Zurich, and Chicago Botanic Garden. This research would not have been possible without Ken Armitage who initiated and led this project from the early 1960’s – one of the longest running mammalian studies. We would also like to thank all the “marmoteers” who contributed to long-term data collection. Nor would it have been possible without Billy Barr and the Rocky Mountain Biological Laboratory for the long-term collection of local environmental data. The study has been funded by the Swiss National Science Foundation, the National Geographic Society, UCLA, a Rocky Mountain Biological Laboratory fellowship, and NSF.
We left behind quite an exciting couple weeks. PopEcol fledged its first cohort of PhDs. Tina, Sam and Koen successfully defended their four years of research and received their doctoral degrees.
They are not only our first PhD fledglings, but also among the founding members of PopEcol. It was difficult to say bye to the trio, who has been with us since the beginning of our group. We can only hope that this separation anxiety gets easier with future fledglings.
We wish them all the best for their future (and very much hope to be a part of that future)! 🙂
Here are the proud carriers of the amazing PhD hats:
Tina Cornioley
Thesis title: “Trait-mediated effects of climate on the population dynamics of the wandering albatross (Diomedea exulans)”
Sam Cruickshank
Thesis title: “Dealing with uncertainty in amphibian and reptile population monitoring for conservation”
Koen van Benthem
Thesis title: “Trait-based mechanistic and phenomenological approaches for predicting population dynamics”
The work field biologists do and the places they do it in blow my mind. The first time I wrote a “Through the Eyes of an Engineer” article was when I went to the Kalahari for the first time, and I thought I had seen all the amazing things that I would ever see in this life. I was happy and ready to settle down and tell my grandchildren these stories while they pulled my contentedly whitening hair. Well, being in Konstanz this past week for the Sixth Bio-Logging Symposium changed all that. With an enigmatic smile, Life brushed away the curtains in front of one of the rooms I hadn’t yet set eyes upon, and streaming rays of awe poured in and filled my consciousness.
The Bio-Logging Symposium is an international conference held every three years where people present findings and techniques related to data obtained through sensors put on/in animals. I’m writing this little piece as a memory of the unbelievable things I saw during this conference and the inspiring people I had the good fortune of meeting and talking to.
Coming from an engineering background, I’ve been conditioned to a world of buildings, shops, computers, graphs, apps and algorithms. This was the world my daily consciousness resided in and took for granted. This conference took this world and compressed it to a pixel in one of the frames of the feature films that is the biological planet we live on, and that’s hidden (fortunately, perhaps) from the eyes of city-dwellers like myself.
I have seen things during this conference that I did not even think about dreaming of. A map of the globe centered around Antarctica was shown in the very first keynote talk by the legendary Gerry Kooyman, who’d spent his entire life working with various animals in the white desert that is the Antarctic. Imagine if you got lost near the South Pole and came across a friendly seal and asked it for directions. Whatever place you’d ask for, the seal would just say, “Oh, it’s up north”, and it would always be right! Talking to Gerry Kooyman a few days later made me rethink the physical references we always take for granted. I asked him how people in the Antarctic managed to avoid crevasses hidden by deceptive, flimsy layers of superficial snow. In response, he told me how broad the issue really was. They could, in fact, not even pinpoint where the horizon was – where the ice ended and where the sky started was anybody’s guess. Even entire hummocks (ice “hills”) would be rendered invisible by the near-complete lack of contrast! Recounting one such episode, he said that once, while driving around in his snow-mobile, he noticed that the engine started straining, and despite going full-throttle, the speed was just not as high anymore. Steeling himself against a slowly sinking heart, fearing a vehicle malfunction, he kept going, and noticed after a while that the engine was back to normal. Curious, he said to himself. He later realised that he’d ridden over a hummock without even seeing it! Recounting a second other-worldly phenomenon, he said he would often chase the green lights of the Aurora Australis on his trusty snow-mobile as they passed over the Antarctic over several minutes.
I saw videos from cameras attached to the backs of elephant seals! Using these cameras, researchers working with National Geographic found that elephant seals would go down to the ocean floor, much lower than they’d earlier expected, to hunt for lobsters scurrying around. This was the first solid proof that protected areas defined for the seals by neighbouring countries needed to extend all the way down to the ocean floor, since the seals will anyway go there to forage, and the protection would only mean something if the entire area traversed by these seals was covered.
As if watching the ocean floor from an elephant seal’s point of view wasn’t spectacular enough, I also met someone from a group in California who put cameras on the back of a blue whale. A blue whale, can you imagine?! For the first time, I got a faint semblance of just how big it really was, and how surprisingly mobile it was for its size. It reminded me of how one has a brief moment of surprise when a plump person turns out to be an excellent dancer. In the video, the blue whale, which one often forgets is actually a predator, made its way determinedly towards a school of fish that had arranged itself into a spherical shape. Approaching the fish, I watched with a quickly dropping jaw as the blue whale reared its head up and opened its gargantuan jaws and swam right through the centre of that school of fish, gobbling up several of them in a single go! This group of researchers had also put gyroscopes and accelerometers on the blue whale along with the camera and saw how these beautiful, massive beasts made banked turns (where they not only turned their head to turn, but also rotated their body around the head-tail axis to make the turn at high speed) during hunting, and slower turns when they were simply sauntering along. What was quite surprising for me was that they actually used the accelerometer and gyroscope to understand what they saw in the videos! In any usual scenario, like with my study with the meerkats, one looks at the video first, observes the activity being carried out by the animal, and then tries to understand the signals recorded by the accelerometer. Puzzled, I asked them what required them to trust the accelerometer and gyroscope more than the video, and they then showed me a video that blew my understanding of deep underwater environments to smithereens. When you are a hundred metres underwater, it is extremely difficult, if not impossible, to gauge just from a picture of the water (from the camera attached to the blue whale) which way is up and which is down! How surprising! Only in some videos, the Sun shone through, and the top part of the video was slightly brighter than the bottom part, and so we could tell which direction was which. The sensors (the camera, inertial measurement units, pressure, temperature and light intensity recorders) were arranged in a cuboidal device with four suction cups on the bottom surface. These suction cups would be attached to the whale’s body. Sometimes, they said that the whale’s skin was as smooth as glass, and the unit would just slip down because the suction cups would just not hold. Other times, the blue whale would just shed a lot of its outer skin, and the cups would get detached along with the shed skin. So many practical challenges! How cool, how awesome! Phffff, I still can’t come to terms with watching the ocean from a blue whale’s perspective!
I learned that polar bears were great swimmers, and that they were truly ‘marine’ mammals. A study in the Arctic waters found a polar bear that swam for seven hundred kilometres straight, continuously over several days! They also showed a rather endearing picture of a little polar bear cub perched atop its mother’s back as it piggy-backed across the frigid waters with its mother swimming at the surface. Since the cubs were smaller and had lesser fat reserves than adults, they couldn’t venture out into the water alone at such an early age – they would just freeze to death otherwise!
Another talk gave, apart from other cool information on Arctic foxes, anecdotal evidence of just how powerful their olfactory senses might be. A truck transporting salmon in Norway had an accident and all the salmon fell in a heap on the ground. The next day, trotting over from more than a hundred kilometres away, a small group of Arctic foxes starting from Sweden had found their way to this site, and happily feasted on this lucky find. Comparing that to human olfactory abilities, I’m generally quite relieved when I realise I need deodorant before others around me start to agree.
Another professor told us about how adult vultures were experts at climbing thermals (to gain altitude in the most energetically efficient way), and how juvenile vultures tended to not do so well, as they would flap their wings at the wrong moment during the ascent and consequently be left far below the adults who were climbing the very same thermal with consummate ease. The adults were apparently very adept at choosing just the right moment to turn their body (approximately every 7 seconds) as they moved upwards in spirals, and the timing of the juveniles was probably off. In fact, that professor actually went on a sabbatical to Australia (or was it New Zealand? I forget) to learn how to fly a glider, and said that the world champions training at the same club he was taking lessons at had independently (probably) figured out that the ideal way to climb the thermals in that part of the world was also to twist the glider around in a spiral and wait for the right moment to turn! Amazing how these vultures had perfected this technique, and that nature had figured out the perfect way to do it all by itself!
Some other examples of the amazing abilities of diverse animals – a researcher using a barometer attached to the back of a sperm whale (I’m going to stop saying just how unbelievable it is that people actually get to interact with such creatures as part of their daily job! “Hey, how was your day?”. “Oh well, you know, the usual. Woke up at 7 am, had some breakfast, popped into the ocean to tag a sperm whale. You?”. “Uh, never mind…”) measured a dive-depth of 3526 m below sea-level (I’m sure about the 3 and 5, but perhaps not about the 2 and 6), which is the deepest dive-depth of a sperm whale measured till date. Three-and-a-half kilometres below sea-level – I’ll probably not be able to hike that distance in an entire day! That’s just unfathomable! Quite literally, I suppose. She did caution us about the precision of this number, since the barometer was close to the maximum amount of pressure that it could measure. Awe is oozing through my nostrils, and I don’t even have the flu.
Another story from a professor from Switzerland tells of a ‘plain, old’ hoopoe flying at a height of 6000 m! Six kilometres above sea-level! That’s as high as mountains in the Himalayas! It must have climbed a (or multiple) thermals on its skyward journey, the professor said.
I learned something else that turned my understanding of the world on its head. Magnetic fields affect the photoreceptors (rods) in our retina, and that modifies the images we see. It could, for instance, introduce a pattern of two broad intersecting lines superimposed on our ‘normal’ field-of-view. The Earth’s magnetic field does this to some animals, and the images that they see when they’re oriented in the north-south direction are apparently slightly different from those they see when they’re oriented in the east-west direction. However, there seemed to be much debate about whether animals actually use these directional differences, and how much of an impact this actually had on animal behaviour, and about how much we could really conclude from the experiments that were done to explore this in foxes.
Experiencing these hitherto hidden corners of the world vicariously through cameras installed in unlikely places has changed my understanding of the world, and the way I felt about this field. I thought I really enjoyed signal processing, and that understanding meerkat behaviour from acceleration data was a beautiful application of it. But this past week made me realise that actually seeing these beings as they go about their daily lives gives birth to a simple, pure feeling of empathy that does not have any logical reason or goal behind it. So many times we hear about heroic animal conservation efforts in articles and interviews, and it does leave us with a warm and fuzzy feeling about the good in humanity, but doesn’t really touch us. Seeing these animals myself over this last week, and actually coming into contact with the people studying with them and hearing them talk about it sort of cracked an outer shell I had in my mind about bio-logging and animal conservation. It is not something separate from our daily lives, not something that happens far away in an unseen corner of a world that doesn’t concern us. People are not unfeeling or self-centered either – they have just not seen! If we could all just simply see the marvel of life around the planet, just simply observe these beautiful beings going about their daily business, we would all just sit with tears streaming down our faces – tears that come from places beyond reason and logic and goals and structure. And empathy would awaken… just like that.
I realised that this was an extension of what the mystic masters say about human life as well – we only feel a need to protect ourselves at all costs (which gets manifested as fear, aggression, comfort- and power-seeking) because we believe in a false sense of identity (our body, our country, our religion) that separates us from the rest of existence. What if all of us were Existence itself? Carl Sagan’s quote comes to mind: “We are a way for the cosmos to know itself”. We are the cosmos itself, and keeping it in good health (as far as our influence extends) is just as natural as perhaps brushing our teeth or taking a bath!
I did not add photos to this post because of two important reasons. First, it’s the difference between watching a film and reading a book – the film feeds you images and doesn’t give you the opportunity or the time to imagine stuff on your own. When you read, however, you stop and visualise, and the work your neurons do to create these inner images opens the doors to memory and emotion (that’s my own opinion, of course). The second important reason why this post doesn’t have any pictures is because I didn’t click any. 🙂
Series of congratulations to Dominik on three wonderful achievements!
First and foremost, he managed to persuade a wonderful lady, Regula, to tie the knot. We wish them a long and happy life together. May they grow old on one pillow!
Secondly, he successfully attracted third-party funding to support his PhD study on wild dog dispersal in Botswana, and started his PhD work. He is currently out and about, gps-collaring wild dogs together with Gabriele.
Last but not the least, he just received the Albert Heim Foundation’s 2016 Science Award, with his MSc work on the Swiss wolves. This award is given annually to outstanding work by young researchers in Swiss universities. The broad spectrum of research includes various disciplines around canines, including interdisciplinary issues such as the human-wolf relationships, which Dominik has nicely studies during his MSc. He sure will be a promising contender again with his new canine sp. in the upcoming years.
This year, our group retreat was in Ticino. It involved ten group members, climbing up 1000m from Mergoscia to Cimetta, staying overnight at the top, and coming back down the next day. A great escape from “winter” in M̶o̶r̶d̶o̶r̶ Zurich. Thanks to Gabriele for organising the retreat and Chris for putting together this video summary:
An epic adaptation of the downfall rant to the capture-mark-recapture world. This was prepared for the retirement symposium of Dr. Jim Nichols, one of the most influential quantitative wildlife ecologists of our times.
Sam won the prize for the best student talk at the Amphibian Conservation Research Symposium (ACRS) with his talk: ““Testing whether conservation action works: does the creation of stepping-stone ponds increase dispersal?”. Criteria were the style of the presentation, the science and the relevance for real-world conservation.
