Butterflies in Flight: a fair-trade delight

Have you ever wondered where the live butterflies in the museum’s popular Butterflies in Flight exhibit come from and how they get here?

Our butterflies are imported from sustainable, fair trade exporters in Costa Rica—the world’s largest butterfly exporter. Recently, I had the opportunity to meet with the museum’s butterfly and plant suppliers there and it was reassuring to meet people so committed to the wellbeing of butterflies! I was able to see how they inspect, sort, and package the pupae and do all the documentation required for legal exportation.

 

The Malachite (Siproeta stelenes) butterfly is one of about three hundred thousand species of Lepidoptera globally. Moths make up the vast majority (95%) of this group, but butterflies are most visible, best known and appreciated. Image: Pierre Poirier © Canadian Museum of Nature

 

One exporter works with more than a hundred different families rearing butterflies sustainably. Smaller family farms specialize in only a couple species of butterflies; others raise many. All Lepidoptera (moths and butterflies) undergo complete metamorphosis, beginning with an egg, then a larva (a caterpillar), a pupa (also known as a chrysalis) and then the adult. The butterflies are shipped as pupae, which are carefully inspected for damage and disease during every step of the processing. The pupae are carefully placed into specialized foam pads; the order is assembled, the pupae checked again.

 

A Postman (Heliconius melpomene) butterfly, one of the many species of Costa Rican butterflies in the museum’s Butterflies in Flight exhibit. Image: Pierre Poirier © Canadian Museum of Nature

 

The pupae are boxed for the destination with all the required paperwork. Costa Rica requires export permits and the museum is required to have import documentation and meet Canadian Food Inspection Agency containment standards. Working together the exporter and farm families ensure the exportation of healthy pupae to museums, zoos and butterfly houses all around the world—the exporter even insulates the shipping box to protect the pupae from the cold during transport.

 

Pupae are carefully sorted by species. Image: Stuart Baatnes © Canadian Museum of Nature

 

When the pupae arrive at the museum, we carefully hang them until they are ready to emerge and then release them into the exhibit, where they fly freely.

In the wild, butterflies feed on more than just flower nectar, often feeding on overripe fruit.  At times, they also feed on dung, urine, blood, and carrion. These unusual foods provide valuable nutrients such as amino acids, salts and other minerals.

 

Pupae are carefully packed for shipment to museums and other centers around the world. Image: Stuart Baatnes © Canadian Museum of Nature

 

To mimic these wild foods in the Butterflies in Flight exhibit, there are several options for feeding. The butterflies can collect nectar from flowering plants or dine at feeding stations which consist of various types of fruit and hanging tubes of red jelly, which provide minerals and sugars to round out a healthy diet.

But even with an ideal diet, adult butterflies have a short lifespan, ranging from a week to a month. Surprisingly, some males can also be fatally aggressive.  And so, from time to time, like the lifecycle of the butterflies, we make another order from our great fair trade, sustainable butterfly suppliers in Costa Rica.

 

The rocks in fishes’ heads tell amazing stories

When I collect and research fish specimens for the Canadian Museum of Nature’s collection, I’m often particularly interested in the rocks in their heads.

These tiny rocky structures, just millimetres in size, are called otoliths, or ear stones. For fishes, otoliths are used for balance and hearing (humans have smaller ear stones used for similar purposes). For scientists, these little otoliths are scientific gold, providing an encyclopedia of information. And, most intriguing of all, fish otoliths hold a few unsolved mysteries.

Otoliths come in pairs, one per ear, and are found near a fish’s brain. The ear stones are composed of calcium carbonate in one of three mineral forms: primarily aragonite; sometimes calcite; and rarely vaterite.

 

The otoliths are clearly visible in this x-ray of an eelpout (unknown species). Image: Noel Alfonso, Stéphanie Tessier © Canadian Museum of Nature

 

The Museum has 2258 otoliths representing 477 species as part of the fish osteological (bone) collection. Researchers use ear stones to investigate biological questions about the fish they came from, ecological questions about the fishes’ environment, and anthropological questions about how people used fish in the past.

Each species of fish has otoliths with a distinctive shape. This means that even when isolated otoliths are found–whether in the gut contents of predators, in feces deposited by animals that eat fish, or preserved on archaeological sites–we can identify the fish they came from.

 

Otoliths of six fish species. From upper left, clockwise: Freshwater Drum (Aplodinotus grunniens) CMNFI Z000082, Red Grouper (Epinephelus morio) CMNFI 1986-67, Northern Pike (Esox lucius) CMNFI 78-166, Atlantic Cod (Gadus morhua) CMNFI 81-836, Goldeye (Hiodon alosoides) CMNFI 1975-1898, Walleye (Sander vitreus) CMNFI Z0000736. Image: François Genier © Canadian Museum of Nature

 

Most importantly, each otolith tells a detailed story about a fish’s life. Otolith size provides an estimate of its body length and the otolith growth rings record a fish’s age and rate of growth in a way analogous to tree rings. The shape of the annual growth rings also captures climatic data, even recording the season of the year when the fish died.

Chemical analysis of otoliths reveals the average water temperature during a fish’s life and the strontium, calcium and zinc ratios in them reveals patterns of migration when fish move from marine to fresh waters, and even within different habitats in large rivers such as the Amazon.

 

Otolith growth rings correspond with the individual’s age. This ear stone of a Black Rockfish (Sebastes melanops) shows that the individual was more than 40 years old. Image: Vanessa von Biela, © USGS (CC BY-SA 3.0)

 

Fish otoliths even help us understand ourselves, in particular our history. For example, a study of heaps of cod otoliths collected from a sixteenth-century Basque fishing settlement in Labrador provided extensive information about Atlantic Cod populations prior to increasingly intensive commercial fishing. Otoliths can be radiocarbon dated to identify when a site was used, and changes in the chemistry and structure of otoliths can even provide information about how a fish was cooked. 

 

Left: Freshwater Drum (Aplodinotus grunniens) otoliths are sometimes called “lucky stones” and made into jewellery. Right: Blog author Noel Alfonso preparing to remove the otoliths of a Greenland Cod (Gadus ogac). Image on left: Brian Coad © Canadian Museum of Nature; Image on right: Noel Alfonso: © Martin Lipman / Students on Ice

 

One of the outstanding fish ear stone mysteries also relates to humans and fish. Farmed fish of all species have ten times the amount of vaterite in their otoliths as compared to their wild cousins, but as yet we don’t know why.

The good thing is that fish have rocks in their heads that help them hear—and help scientists like me tune into amazing natural history stories.

Lemmings: The favourite Arctic meal

The Arctic tundra is home to a small animal whose ecological footprint is much larger than its size would suggest – the lemming. In many summers, these slightly larger-than-a-mouse mammals are the most sought-after meal in the Arctic. In fact, lemmings are part of a complex food web that has an impact across North America and beyond.

A brown lemming (Lemmus trimucronatus) on Bylot Island, Nunavut. Dominique Fauteux © Canadian Museum of Nature

Lemmings are famous for having dramatic boom-and-bust population cycles.

Every three to four years, lemmings hit a population cycle peak, when the population density can increase from a low of one lemming per hectare to a high of as many as 100 lemmings per hectare. The range of population peak depends on whether the lemming populations are located in the Canadian Arctic Archipelago (Nunavut) or in more productive areas in Alaska, Yukon, and the Northwest Territories.

The Centre for Northern Studies’ Bylot Island Research Station in Nunavut, an ideal location for studying lemmings. Dominique Fauteux © Canadian Museum of Nature

The mechanisms driving these cycles are complex, including the amount of summer predation on lemmings and their winter food availability, including willows and mosses. According to Canadian scientists, the most likely hypothesis is that dramatic population declines are caused by intense predation, whereas phases of population growth are dependent on successful winter reproduction. For example, research has shown that lemmings in Canada’s High Arctic reach population peaks only when they achieve high rates of winter reproduction.

During peak lemming population years at a given location, a notable phenomenon occurs: the majority of tundra birds and mammals, carnivores and herbivores alike, reproduce successfully.

One reason for this is that, during peak population years, lemmings are an abundant food source for snowy owls, rough-legged hawks, long-tailed jaegers, gulls, Arctic and red foxes as well as ermines. While the lemmings are being hunted en masse there’s less predation pressure on geese, passerines and shorebirds.

One of the lemming’s many predators, the long-tailed jaeger (Stercorarius longicaudus). Dominique Fauteux © Canadian Museum of Nature

Consequently, the well-fed predators and less hunted prey species successfully reproduce, with North America-wide implications. For example, the resulting increase in snow goose populations has a positive impact on the hunting season in Quebec and the United States.

Thus, despite their small size, lemmings have a huge ecological footprint.

 

 

Whale composting: Letting bacteria do the hard work of specimen defleshing

Bones and skeletons are key parts of a natural history collection, used by researchers from archaeologists to zoologists. Usually, preparing these osteological specimens starts with removing the flesh. No big deal for small animals.

But, a couple of years ago, Canadian Museum of Nature collections staff faced a whale-sized specimen preparation challenge.

We wanted to deflesh hundreds of kilograms of preserved whale specimens. They had been collected during commercial whaling off the coast of Newfoundland from the late 1960s until 1972, when commercial whaling in Canada was ended.

These specimens weren’t just big (up to 25 kilograms) they had also been changed by the preservation process.

Before being transferred into ethanol in the late 1990s, the whale parts had been stored in formalin which hardens animal tissues. This meant they’d require additional preparation, such as ammonia soaks or peroxide treatments, to break down the tissues so that they could be physically removed.

We calculated that manually removing the skin, blubber and muscle to preserve the bones would take years.

Our short-cut alternative? Compost the whale pieces and let bacteria and fungi do the hard work of defleshing.

Whale specimens in the museum’s special compost bin prior to being covered with sawdust and manure. Image: Shalini Chaudhary © Canadian Museum of Nature.

So, in the summer of 2017 we created a compost station on the grounds of the museum’s research and collections facility in Gatineau.

Efficiently composting large whale pieces requires creating a compost pile with the right mix of carbon (sawdust) and nitrogen (manure) to achieve the ideal temperature for microorganisms, and then giving it time.

During the summer, we did five 18-day composting cycles. During each cycle, we adjusted the sawdust to manure ratio to try and achieve the ideal temperature, which varied between 27°C and 43°C. Sometimes we added water to optimize the humidity levels for the microorganisms. After the last cycle, we removed the largely defleshed whale pieces from the compost pile and moved them into the collections lab.

The compost-based defleshing process did not go as quickly, or work as completely, as we’d anticipated. This was in part because we’d struggled at times to reach optimal composting temperatures. So, to get rid of the remaining flesh we simmered the bones in almost-boiling water, a technique called hot macerating. Then, residual oil was removed by soaking in ammonia. Finally, a peroxide soak bleached the bones which had darkened in the composting process.

A chart of ambient air temperature vs. the internal compost temperatures over three months during whale specimen composting. The most efficient composting occurred when there was the largest gap between the two temperatures. Image: Marie-Hélène Hubert © Canadian Museum of Nature

This combination of multiple preparation techniques worked well and saved the museum time, money and effort. Osteological, or bone, specimens are important components of natural history collections. They are used by many researchers, from archaeologists and palaeontologists to comparative anatomists and zoologists. So, there will always be work preparing these specimens.

Our whale composting experiment has led us to think that we might well be heading back to the compost heap for the preparation of future zoological specimens.

Fin whale (Balaenoptera physalus) skull bones before (left) and after (right) composting. The initial weight was 25 kg; after composting and cleaning, 18.7 kg. Image: Marie-Hélène Hubert © Canadian Museum of Nature.

Dendrites in rock: Getting a microscopic view

Last summer, I had my first research job: a geology summer student at the Canadian Museum of Nature as part of its Scientific Training Program. It was an incredible experience. At first, though, I was very nervous. Thankfully, the work environment was very student friendly which took away my fear of messing up.

Throughout the summer I was given lots of opportunities for hands-on tasks. My favourite was learning how to operate the museum’s Scanning Electron Microscope (SEM). With this technology, I looked at minerals 20-times smaller than the width of a human hair. It was fascinating to see how crystal structures stay the same, whether it’s a mineral 0.002mm small or one 20m tall.

A magnesium oxide dendrite in a specimen from the Pilbara Region of Western Australia. Field of view 0.44mm. Image: Ann Presley © Canadian Museum of Nature.

During my SEM work with museum researcher Aaron Lussier I had the opportunity to examine rock samples from around the world. However, my research mainly involved samples of chalcedony, a variety of quartz, from the Pilbara region of Western Australia. The focus of my summer research was studying how elements, such as iron, move through this rock. For example, why only certain elements are incorporated into the rock’s structure.

Similarly, another question I explored is why the minerals grow the way they do, including the interesting behaviour of dendrites in chalcedony. A dendrite is a natural tree-like or moss-like formation on, or in, a piece of rock or mineral. A dendritic pattern forms when an element or mineral, starting from a point of origin, migrates and branches outward. A single dendritic branch extends until the mineral reaches a point where growing various new branches is, for some unknown reason, more favourable.

A magnesium oxide dendrite in a limestone specimen from Solnhofen, Germany. Catalogue number CMNMC 34359. © Canadian Museum of Nature.

Dendritic branching is just one of the many natural phenomena scientists like myself hope to explain in the future. My museum internship was such a fun, amazing and memorable learning experience — one for which I am very grateful as I branch-out on my research career.

 

Bees and Wasps: Providing Ecosystem Services with a Point

With spring finally on the way, many of us are excited about patio season. So are some wasps. It’s an almost sure bet that in late summer yellowjackets of the genus Vespula will be unwanted visitors at our outdoor picnics and barbecues. Even though I’m a hymenopterist – someone who studies bees and wasps, currently the museum’s Beaty Postdoctoral Fellow for Species Discovery – I too can be bothered by yellowjackets as they relentlessly hover around my plate and drink.

But while there’s lots of buzz about bees’ ecological and economic importance, it’s unfortunate that our appreciation of wasps’ enormous ecological role is overshadowed by a few species that disrupt our outdoor dining.

What are wasps? They include more than 100 000 members of the insect order Hymenoptera with a narrow “waist” that are not bees or ants.

A female baldfaced hornet, Dolichovespula maculata, a widely distributed and commonly encountered species of North American wasp. Image: François Génier, © Canadian Museum of Nature.

Wasps are essential for ecosystem functioning and indirectly responsible for increased food production. Most wasp species prey on other insects, including agricultural pests (the ones hovering over your drink are adults in search of a sugar fix to fuel their flight). Some wasps are parasitoids, laying eggs in other insects. After hatching, the offspring feed on those insects. These wasps in particular are a desirable and effective alternative to pesticides as they go after specific insect targets without any risk of environmental contamination.

Many wasps are also essential pollinators. Figs, for example, are pollinated by minute, specialized wasps.

Although very wasp-like, this is a female cuckoo bee (Nomada sp.). Cuckoo bees invade the nests of foraging bee species, stealing their pollen. The absence of long pollen-collecting hairs is due to their cleptoparasitic lifestyle. Image: Thomas Onuferko, © Canadian Museum of Nature.

Bees are effectively vegetarian wasps and include more than 20 000 species. Unlike wasps, bees have small, branched featherlike hairs which help to pick up flower pollen, the protein-rich food source on which their brood is reared, and in turn pollinate flowers.

However, not all bee species are important pollinators. About 15% of bees are “cuckoos” — they invade the nests of other bee species stealing pollen for their own offspring.

The flowers of the scarlet globemallow (Sphaeralcea coccinea) attract many kinds of bees. Image: Thomas Onuferko, © Canadian Museum of Nature.

So, what about the fear of getting stung by a wasp? Yes, female yellowjackets can inflict a painful sting (the males don’t have stings). But the majority of wasp species don’t sting.

Many female bees and some ants also have stings, but they generally do not elicit strong negative feelings. We see bees as seemingly docile compared to wasps, even though social bees can be quite dangerous when defending a nest.

Bees and wasps both play vital roles in the production of much of the food we eat. The pollination of plants by bees enhances fruit production. Wasps help keep pests away, reducing competition for our food.

So, the next time that wasps are bugging you, it might help to recall that without them, your meal might look very different.

Herbarium Sheet Mounting: Adhesives Recommendations That Really Stick

In the summer of 2018 Jennifer Doubt, the museum’s botany curator, presented me with a challenge: find a better adhesive for mounting the museum’s botany specimens on herbarium sheets.

I was working in the museum’s Conservation lab as part of the Scientific Training Program, but my background is in fine arts, and conservation training with materials including metal, wood, textile, and paper conservation—not conserving ferns and flowers. Natural history conservation is specialized and rarely taught in conservation programs in Canada. So, I was excited for the opportunity to challenge myself in something new.

Having the best possible adhesive is critical because every year the botany team adds more than 5,000 specimens to the museum’s National Herbarium of Canada which includes more than 650,000 herbarium sheets in the vascular plant collection. At present, new specimens are attached to herbarium sheets using linen tape, a process that’s effective, but very time consuming. My task was to find a conservation glue that’s easy and quick to apply and keep specimens stuck for a long time.

Notice the missing section of this spreading wood fern (Dryopteris expansa). Over time the adhesive holding the specimen to the herbarium sheet aged and failed, resulting in the loss. Specimen collected in 1895. Catalogue number CAN 10005210. Image: © Canadian Museum of Nature.

This alpine hedysarum (Hedysarum americanum) is attached to its herbarium sheet with linen tape. This technique allows the plant to bend with the sheet, decreasing the risk of breakage and loss. But applying linen tape is a time-consuming process, with each piece of tape carefully cut and placed by hand. Specimens collected in 2016. Catalogue number CAN 10042881. Image: © Canadian Museum of Nature.

My core challenge was that in the conservation literature there’s no single recommended adhesive for herbarium collections. So, in my search for the best adhesive I considered the museum’s needs while exploring new research in adhesives.

Three of the key herbarium conservation needs are strength, flexibility, and neutral pH. Herbarium specimens must be conserved for decades, if not centuries. So an adhesive must have enduring strength to hold a specimen on its sheet and also flexibility to keep it held while the sheet’s handled by researchers.

A neutral pH keeps the surrounding substrate from becoming acidic, turning yellow, and prematurely aging.

This closeup image of a subalpine fir (Abies lasiocarpa) herbarium sheet shows that the adhesive has browned with age masking some of the specimen from view. The browning also indicates that the adhesive’s become acidic, which could cause damage to the area over time. Specimen collected in 1975. Catalogue number CAN 10005767. Image: © Canadian Museum of Nature.

In addition to these archival requirements, the adhesive I was looking for also needed to have other practical properties. It needed to be water-based, high tack, and clear when dry.

The Canadian Conservation Institute’s long-term study of commercially available adhesives, Adhesive Compendium for Conservation was an invaluable resource.

My research led me to recommend three neutral pH polyvinyl acetate (PVA) adhesives or “white” glue.  These adhesives have both great workability properties in the lab and long-term preservation qualities. They have stood the test of time while remaining strong, flexible, neutral, and exhibiting minimal yellowing.

My adhesive research truly stuck with me. It enabled me to more deeply appreciate how in the selection of conservation materials every small detail must be considered to ensure the preservation of collections.

Understanding material characteristics and their deterioration was a core concept in my conservation training. I’m proud to know that what I contributed to the museum’s herbarium will increase the chance that in the 22^nd century a museum botanist will hold a herbarium sheet prepared today—with its specimen still firmly attached.

In Jassa mating: A thumb matters

This year marks the 30^th anniversary of my Ph.D.-related publications about tiny, shrimp-like animals called Jassa. I set out to discover a way to tell the species apart based on their appearance. But soon I asked why they looked that way.

Blog author and museum scientist Kathy Conlan in 1980 searching for Jassa in a sample collected in southeastern Alaska. Image: Ron Long, © Canadian Museum of Nature

First, a little about Jassa. It’s a genus of 20 species of marine, colonial amphipods, in which each male or female lives in a self-made tube that it attaches to almost anything hard, from rocks and docks to boat hulls. Species of Jassa live on most rocky shores and harbours around the world from Newfoundland to the Antarctic (not yet in the Arctic, but see Cruising the Globe Undetected). Anchored in their tubes, they extend into the water to capture passing plants and animals or scrape up bits of dead organic material called detritus. Being without a tube could be a death sentence as Jassa is easy prey to fishes.

A female Jassa marmorata in her tube. Her four antennae are outstretched to capture passing phytoplankton, zooplankton and detritus. Image: Kathy Conlan, © Canadian Museum of Nature.

Yes, it’s mostly a sedentary life, but things get interesting when it comes time to mate.

Inside its tube, Jassa grows in stages, splitting its old outer “skin”, or cuticle, after it has grown a new, slightly larger one inside, a process called molting. For a mature female, this is the only time that her cuticle is flexible enough to allow the release of her unfertilized eggs into her external brood pouch. For a mature male, this is the only time that he can fertilize her eggs.

This opportunity to mate is very short, only a couple of hours long. So there is fierce competition among adult males to find a female that is receptive to mating. The females broadcast their receptiveness by releasing attractive chemicals. The adult males abandon their tubes, roving to find the receptive females. But the females are choosy. They will only accept males with the right look. These males have to have a thumb (an enlargement on a gnathopod, or pincer). The thumb signals an intent to mate. Thumbless males are intent on evicting the female from her tube, and so she drives them off.

The thumbed males fight to guard the receptive female until she is ready to molt and release her eggs. Once fertilized, the embryos grow inside the eggs until hatching as miniature Jassas.

Confrontation between two large-thumbed male Jassa marmorata. Image: Kathy Conlan, © Canadian Museum of Nature.

In my doctoral research, I discovered that not all Jassa thumbs are alike. In every species, big males had big thumbs but some little males had smaller thumbs than would be expected for their body size. Some also had ornaments that the big males did not have. I thought this might indicate that the little males behaved differently and follow-up studies by other scientists have confirmed this for Jassa marmorata.

The little males appear when there has been not much protein from phytoplankton and zooplankton to feed on, so they had to depend on a less healthy diet of bits of detritus. But what little thumbed males lack in size, they sometimes make up for in behaviour.

A male Jassa marmorata with a major thumb on its gnathopod (below and to the right of its head). The size of the adult male’s thumb seems to depend on its diet. A well-fed big “major” male produces a big thumb. Nutrient poor environments result in small “minor” males with smaller thumbs than expected for their body size. Image: Susan Laurie-Bourque, © Canadian Museum of Nature.

Faced with a big male with an over-sized thumb, the little males seemingly don’t stand a chance. But in fact, they do. They are quick to mature and their small thumbs are big enough to signal the female not to reject them. When they outnumber the big males, they win the mating. And females will accept more than one male to mate with, increasing the odds that little guys can succeed too.

So, different strategies work for different situations. The fascinating Jassa mating ritual dances to the rhythm of how a male presents his thumb.

 

A possible new species almost found — but lost

Several years ago a colleague sent me two specimens of blind cave fish collected in the Zagros Mountains of western Iran. I was intrigued. The specimens were small, just 2.5 centimetres long, and in very bad condition. But I could tell they belonged to the cyprinid genus Garra — and there were hints they are probably a new species to science. But, we’ll probably never know, and to explain why requires some background context.

Cave fishes are fascinating creatures whose habitat is usually the water in limestone caves, including tiny cracks between rock layers, and often occurring over very wide areas. Blind cave fish are related to species living in nearby streams and rivers. But, in the absence of light deep underground, there’s no advantage in maintaining eyes and sight. They’ve also lost skin pigmentation, appearing pink, a result of blood visible through their unpigmented skin. The blind cave fishes are thus different species, clearly defined by their DNA.

The Iranian cave barbs Garra lorestanensis and G. typhlops are blind cave fishes similar to the unidentified specimens sent to museum fish expert Brian Coad. Image : Ruhollah Mehrani, © Lorestan Research Centre of Natural Resources and Animal Science, Khorramabad, Iran.

Four species of blind cave fishes are known to exist in the Loven and Tashan caves in Iran, including three members of the Cyprinidae family (carps) and one of the Nemacheilidae family (loaches). However, these sites are respectively about 130 and 270 km away from where the new specimens were collected, heightening the possibility the specimens represented a new species.

Dip netting for fish at the Loven cave in Iran. Image: Brian Coad, © Canadian Museum of Nature.

Since the specimens were in poor condition, the only way to solve the mystery was to collect more. Unfortunately, this is no longer possible. They were collected from a shallow pool formed from water seeping from a rock face when a tunnel was drilled through a mountain during construction of the Simareh dam in 2005. The tunnel where they were collected in now buried, encased in concrete.

Faced with this dead-end, we thought we might be able to solve the question by examining the DNA of the specimens and comparing it to that of known Iranian cave fishes DNA available in an online database. Despite the valiant efforts of the museum’s DNA specialist Roger Bull, this route also failed. The fishes’ genetic material was damaged beyond recognition by time and its initial preservation in formalin.

Thus, it appears that this possible new species of blind cave fish may have been lost to science before it was truly found.

Yet, ironically, currently buried under hundreds of metres of rock and concrete, it may now be safe from any further ravages, whether natural or human-caused.

Champsosaurus: CT scanning reveals its ear openings really were on the bottom of its skull

At Ottawa’s Alta Vista Animal Hospital, when an animal gets a CT scan it’s usually a cat or dog and the vet is looking for broken bones or tumours.

But I brought a Champsosaurus, and I wanted a CT scan to look for its ears.

Let me explain. The up to two-meter long Champsosaurus was a genus of aquatic reptile that lived from 90 to 55 million years ago. Champsosaurus resembled modern crocodiles, but is only distantly related to them, and has no descendants alive today.

A large specimen of Champsosaurus natator, a species that lived in western North America from about 70 to 66 million years ago. On display in the Fossil Gallery at the museum. Catalogue number: CMNFV 8919. Image: Thomas Dudgeon, © Canadian Museum of Nature.

So, what we know about Champsosaurus comes from its fossil remains, and this leads to the ear problem.

Champsosaurus had a relatively delicate skull, with a long and slender snout and large arches of bone at the back of the skull that anchored jaw muscles. The skull was so fragile that few are well preserved, and thus little is known about the finer internal structures such as the braincase and the inner ear.

Top view of a well-preserved Champsosaurus skull in the Canadian Museum of Nature collection. Fun fact: Scientists call heart-shaped objects cordiform. Tilt your head to the right and see how the long snout and large arches of bone give Champsosaurus a heart-shaped skull. Catalogue number: CMNFV 8920. Image: Thomas Dudgeon, © Canadian Museum of Nature.

However, in the 1950s, museum palaeontologist L.S. Russell suggested that holes on the bottom surface of the Champsosaurus skulls were the ear openings. As you can imagine, this is a strange place for ear openings to be, and not all palaeontologists were convinced. Although some animals, like a few salamander species, have ear openings on the bottom of their skulls, most animals, including humans of course, have ears on the sides of their skulls.

So, as part of my Master’s thesis in Carleton University’s Department of Earth Sciences, I decided to tackle the mystery of whether the Champsosaurus’ ears really were on the bottom of its skull.

Fortunately, there are two well-preserved skulls of Champsosaurus in the Canadian Museum of Nature’s palaeo collection.

A Champsosaurus skull ready to go through a CT scanner at Ottawa’s Alta Vista Animal Hospital. Catalogue number: CMNFV 8919. Image: Thomas Dudgeon, © Canadian Museum of Nature.

I carefully transported one skull to the Alta Vista Animal Hospital for a much overdue check-up, and the other was sent to the University of Texas CT facility for scanning. CT scanning is a medical technique that uses X-rays to create hundreds of thin cross-sectional images, providing a detailed view of the internal structures.

When I examined the CT scans of the Champsosaurus skulls, to my surprise and excitement, I discovered that the openings on the bottom of the skull do indeed lead to the inner ear.

A line drawing of a Champsosaurus skull in bottom-view, ear openings highlighted in blue. Catalogue number: CMNFV 8920. Image: Thomas Dudgeon, © Canadian Museum of Nature.

This of course raises the question of why Champsosaurus’ ear openings were on the bottom of its skull. It may have been due to the fact that the large arches of bone at the back of the skull were so prominent they displaced the ear openings from the side to the bottom.

To explore other possibilities, and how this influenced its hearing, I’m now comparing Champsosaurus ear anatomy to that of modern reptiles and amphibians.

I hope it will give me a sense of what this intriguing Cretaceous creature could hear with ears on the bottom of its skull.