I see foxes pretty frequently around here. I happened to glance out the window earlier today, and there was a rather mangy fox in the tiny garden behind my building. I’ve noticed that most of the foxes around here don’t seem to be doing very well, which is why I was a bit surprised to learn that in general, they thrive in cities. Back in the US, urban mid-sized mammals would be a mix of skunks, possums, raccoons, and the occasional fox or coyote. Out of all of those, the only ones that live on these islands are the foxes, and they do seem to have filled in that slot. While they all look a little ratty, there are foxes everywhere around here. Anyway, all of this was to provide a bit of an intro to this video from Casual Geographic, telling us about foxes, and how they took over the world.

My understanding of the mammals that lived when the (non-avian) dinosaurs were still around, was that they were generally little rat-like critters that lived generally little rat-like lives, as omnivorous scavengers and opportunists, that also served as prey. Apparently, my education on dinosaur-mammal relations has been lacking, because apparently there were mammals that ate dinosaurs. This seems to be something that paleontologists have known for a while, but they recently found a fossil in China’s “Dinosaur Pompeii” of a Cretaceous Psittacosaurus in the process of being killed and eaten by a Repenomamus:

“The two animals are locked in mortal combat, intimately intertwined, and it’s among the first evidence to show actual predatory behaviour by a mammal on a dinosaur,” explains Dr. Jordan Mallon, palaeobiologist with the Canadian Museum of Nature and co-author on the study published today in the journal Scientific Reports.

The fossil’s presence challenges the view that dinosaurs had few threats from their mammal contemporaries during the Cretaceous, when dinosaurs were the dominant animals. The rare fossil is now in the collections of the Weihai Ziguang Shi Yan School Museum in China’s Shandong Province.

The dinosaur in the well-preserved fossil is identified as a species of Psittacosaurus, which is about the size of a large dog. Plant-eating psittacosaurs are among the earliest known horned dinosaurs and lived in Asia during the Early Cretaceous, from around 125 to 105 million years ago.

The mammal in the fossil pair is a badger-like animal, called Repenomamus robustus. Although not large by dinosaur standards, it was among the largest mammals during the Cretaceous, at a time when mammals had not yet come to dominate the Earth.

Prior to this discovery, palaeontologists knew that Repenomamus preyed on dinosaurs including Psittacosaurus because of fossilized baby bones of the herbivore found in the mammal’s stomach.

“The co-existence of these two animals is not new, but what’s new to science through this amazing fossil is the predatory behaviour it shows,” says Mallon.

The image is an artist’s rendition of the moments before the two animals were killed by the volcanic mudslide. The Psittacosaurus is a stocky, beaked dinosaur, with longer hind legs than fore, and a thick tail. It’s braced on three legs, with one front limb raised to ward off the attacking mammal. The Repenomamus, a badger-like mammal appears to be leaping onto the unfortunate dinosaur, climbing up onto it like a weasel attacking a hare. The two animals are fighting against a stump, with trees in the background, and smoking volcanoes in the distance.

It’s nice to know that eating dinosaurs is about the oldest tradition we have, as mammals.

I’m procrastinating on a couple of rather grim posts, and I was looking for something chill to write about on this cool and rainy day, when I came across something rather astonishing. I want to say that while I do think sharks are really cool, they’ve never really been a special interest of mine. That’s why it strikes me as odd that I am now writing a third post about sharks and temperature, none of which have had anything to do with global warming. It started with the recent eruption of the Sharkcano, and we learned about sharks that make their living in and around the natural hot tub of an active volcanic crater. Then, there was the discovery that hammerhead sharks hold their breath to dive, to avoid being chilled by the cold of deeper waters.

And now, we have the novel discovery that basking sharks are warm-blooded, after a fashion. Basking sharks are filter feeders, like whale sharks, megamouths, and baleen whales. They’re big – second only to the whale shark – fairly slow-moving, and they just cruise around, inhaling copepods. They are also, we now know, one of the vanishingly small minority of fish that internally regulate their own body temperature, and it was discovered right in my back yard!

The image is a color-adjusted photo of a basking shark, and frankly it looks like something from a cartoon. The shark is swimming from right to left, and its head is closer to the camera than its tail. This slightly exaggerates the size of its head, but not by much. It looks as though someone took a relatively ordinary shark, and gave it a giant muppet-like shark hat to wear. It has a large, bulbous nose, with two small eyes behind it. Below is a massive, gaping cavern of a mouth, that acts as a trawling net as the rest of the shark pushes the mouth around. This is less of a shark, and more of a mouth with a shark attached to it. It’s near the surface, so the sunlight is forming a pretty dappled pattern on its gray-brown skin. This image was uploaded to Wikimedia Commons by Greenfire Productions.

Approximately 99.9% of fish and shark species are “cold-blooded”, meaning their body tissues generally match the temperature of the water they swim in – but researchers have just discovered the mighty basking shark is a one-in-a-thousand exception.

Instead, these sharks keep the core regions of their bodies warmer than the water like the most athletic swimmers in the sea such as great white sharks, mako sharks and tuna.

The latter examples are so-called “regional endotherms” and are all fast swimming, apex predators at the top of the food chain. Scientists have long reasoned that their ability to keep warm helped with this athletic predatory lifestyle, and that evolution had shaped their physiology to match their requirements.

However, an international team of researchers led by those from Trinity College Dublin, has now shown that gentle, plankton-feeding basking sharks are also regional endotherms despite having very different lifestyles to white sharks and tunas.

This surprising discovery has implications for conservation, as well as raising a plethora of ecological and evolutionary questions.

Haley Dolton, PhD Candidate in Trinity’s School of Natural Sciences, was lead author of the study that has just been published in international journal, Endangered Species Research. She said:

“The basking shark is a shining example of how little we know about shark species in general. That we still have lots to uncover about the second biggest fish in the world – such a huge, charismatic animal that most people would recognise it – just highlights the challenge facing researchers to gather what they can about species to aid in effective conservation strategies.”

Basking sharks gained legal protection in Irish waters just last year, with the species having undergone significant population declines throughout the NE Atlantic in the last century. But they still face many challenges in the future.

Haley Dolton added: “Regional endotherms are thought to use more energy, and possibly respond differently to ocean warming than other fish species. So lots more work will need to be done to work out how these new findings regarding an endangered species might change previous assumptions about their metabolism or potential distribution shifts during our climate crisis, which is something marine biologists are focusing on as our planet and its seas continue to warm. 

“Hopefully this kind of research will continue the momentum needed to effectively protect these incredible animals in Irish waters and further afield.”

Well, ok, it is a little about global warming, because everything is during a catastrophic warming event, but the sharks were doing this before we started mucking up the atmosphere. It seems as though a lot of the heat is generated by their primary “drive shaft” – the cruising muscles that keep them constantly moving forward, but I hadn’t realized that the ability to heat your own body is reflected in how your heart’s put together:

To make the discovery, the research team (including scientists from University of Pretoria, Marine Biological Association, Queen’s University Belfast, Zoological Society of London, University of Southampton, and Manx Basking Shark Watch) first undertook dissections of dead basking sharks that washed up in Ireland and the UK.

They found that the sharks have cruise-swimming muscles located deep inside their bodies as seen in white sharks and tunas; in most fish this “red” muscle is instead found toward the outside of the animals.

They also discovered basking sharks have strong muscular hearts that probably help generate high blood pressures and flows. Most fish species have relatively “spongy” hearts, whereas basking shark hearts are more typical of the regional endotherm species.

Next, the team designed a new low-impact tagging method to record body temperature of free-swimming basking sharks off the coast of Co Cork, Ireland. Researchers were able get close enough to 8 m basking sharks to safely deploy the tags, which recorded muscle temperature just under the skin for up to 12 hours before they automatically detached from the animals and were collected by the researchers.

These tags revealed that basking shark muscles are consistently elevated above water temperatures, and to almost exactly the same extent as their regionally-endothermic predatory cousins.

Nicholas Payne, Assistant Professor in Trinity’s School of Natural Sciences, was senior author of the study. He said:

“These results cast an interesting new light on our perception of form versus function in fishes because until now we thought regional endothermy was only found in apex predatory species living at high positions in the marine food web. 

“Now we have found a species that grazes on tiny plankton but also shares those rather uncommon regional endotherm features, so we might have to adjust our assumptions about the advantages of such physiological innovations for these animals.

“It’s a bit like suddenly finding that cows have wings.”

As Dolton said, it’s a good reminder of how little we know; not just about sharks, but about oceanic life in general. For all the problems in the world, I’m glad to live in a time when I get to learn new things like this.

When people talk about the decline in insect populations, the focus is generally on pesticide use, and habitat destruction. There’s no question that these are major factors, but there’s another that has apparently been under-estimated: air pollution. I talk about air pollution a lot on this blog, and while that’s mostly focused on how it affects humans, I did post last November about how air pollution made it harder for fig wasps to find their aphid prey. The researchers speculated that the presence of diesel fumes and ozone masked the scent of their prey, but that prey feeding on cabbages and other brassicas were smelly enough to cut through the pollution. Now a new study has come out, which demonstrates that air pollution particles can collect on an insect’s sensory organs, affecting their sense of smell in general:

The research team conducted several related experiments:

• Using a scanning electron microscope, they found that as air pollution increases, more particulate material collects on the sensitive antennae of houseflies. This material comprises solid particles or liquid droplets suspended in air and can include toxic heavy metals and organic substances from coal, oil, petrol, or woodfires.
• They exposed houseflies for just 12 hours to varying levels of air pollution in Beijing and then placed the flies in a Y-shaped tube ‘maze’. Uncontaminated flies typically chose the arm of the Y-maze leading to a smell of food or sex pheromones, while contaminated flies selected an arm at random, with 50:50 probability.
• Neural tests confirmed that antenna contamination significantly reduced the strength of odour-related electrical signals sent to the flies’ brains – it compromised their capacity to detect odours.

In addition, continuing research in bushfire-affected areas in rural Victoria has shown that the antennae of diverse insects, including bees, wasps, moths, and species of flies, are contaminated by smoke particles, even at considerable distances from the fire front.

Insect antennae have olfactory receptors that detect odour molecules emanating from a food source, a potential mate, or a good place to lay eggs. If an insect’s antennae are covered in particulate matter, a physical barrier is created that prevents contact between the smell receptors and air-borne odour molecules.

“When their antennae become clogged with pollution particles, insects struggle to smell food, a mate, or a place to lay their eggs, and it follows that their populations will decline,” Professor Elgar said.

“About 40 per cent of Earth’s landmass is exposed to particle air pollution concentrations above the World Health Organisation’s recommended annual average.

“Surprisingly, this includes many remote and comparatively pristine habitats and areas of ecological significance – because particulate material can be carried thousands of kilometres by air currents,” Professor Elgar said.

I’ll be honest: If you had asked me how air pollution was contributing to the decline in insect populations, I would have guessed ill health through inhaling, drinking, or eating air pollution, but I wouldn’t have gone with “it messes with their sense of smell”. Given the fig wasp thing I mentioned above, I guess it should have been higher on my list, but I apparently didn’t give it enough thought. I think it’s partly that being a visual creature that gets food from stores, I sometimes forget the importance of smell to other animals. Repetition aids memory, though, so now I’m more likely to remember it. I suppose the next question here will be how big this olfactory problem is, but while we wait for a number, we can add this to the already-huge pile of reasons why it’s good to reduce air pollution.