Brian Tanis
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tanisbp.bsky.social
Brian Tanis
@tanisbp.bsky.social
360 followers 160 following 86 posts
Ecology & Evolution at big scales
All-around nature enthusiast
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tanisbp.bsky.social
My favorite part of this image is the seal at the bottom in the water avoiding being polar bear prey & thinking "lol get wrecked" #2025MMM
A line-drawing from 1877 depicting a sad looking narwhal fully out of the ice while a happy polar bear is walking up for an easy meal. A tiny seal pokes its head out from the water nearby to witness the scavenging.
March 28, 2025 at 1:49 AM
tanisbp.bsky.social
AS FORETOLD in 1877!!! commons.wikimedia.org/wiki/File:An...
A line-drawing from 1877 depicting a sad looking narwhal fully out of the ice while a happy polar bear is walking up for an easy meal. A tiny seal pokes its head out from the water nearby to witness the scavenging.
March 28, 2025 at 1:26 AM
tanisbp.bsky.social
Seeing the Narwhal stranded in the shallow pool, polar bear re-calculates the odds of a successful hunt & moves in fast for a FEAST! After all, spring is the MAIN GORGING season of Polar Bears that will continue to consume meat available many days in a row! #2025MMM
Scavenging: a polar bear (Ursus maritimus) eating flesh from a narwhal whale carcass (Monodon monoceros). A wet-looking bear standing in shallow water along a rocky shore is tearing flesh off a large carcass (Photo: Jeff W. Higdon/DFO). doi:10.1371/journal.pone.0060797.g001 from Fallows C, Gallagher AJ, Hammerschlag N (2013) White Sharks (Carcharodon carcharias) Scavenging on Whales and Its Potential Role in Further Shaping the Ecology of an Apex Predator. PLoS ONE 8(4): e60797. doi:10.1371/journal.pone.0060797
March 28, 2025 at 1:25 AM
tanisbp.bsky.social
SPECIFICALLY the Tauranga geothermal system adjacent to the Bay of Plenty in Aotearoa / New Zealand! (Carden et al. 2024; de PS Zuquim et al. 2022) #2025MMM
Image adapted from Zuquim et al. 2022 showing the geothermal system of the Turanga region. Text within reads: “Figure 4: Thermal gradient distribution and location of the warm springs in the TGS. The black dots are the data points for contouring the thermal gradient.” An insert has been added with silhouettes of narwhal and polar bear and the battle location.
March 28, 2025 at 1:21 AM
tanisbp.bsky.social
Polar Bear turns to refocus on Cape Buffalo carcass…WHEN SUDDENLY AN ORCA STREAKS TOWARD THE NARWHAL! #2025MMM
Photo of an orca speeding along the surface of choppy water. Water crashes over its smooth black back and races past its large dorsal fin. Image from NOAA
March 28, 2025 at 1:18 AM
tanisbp.bsky.social
But a smart bear knows the odds… targeting a large male narwhal with room to swim away is a waste of energy than a filling meal. Narwhal in the diet of most polar bears comes from scavenging individuals that died navigating gaps in the ice (Galicia 2021) #2025MMM
Meme of polar bear calculating as a play on the “math lady” meme. Meme depicts four panels of polar bear with calculations and a geometric narwhal dancing around its head. The calculations include scientifically acurate depicticions of lever arm ratios for an ursid mandible, formulas for calculating maximum bite force quotient and, calculations for wave dynamics.
March 28, 2025 at 1:17 AM
tanisbp.bsky.social
While typically cetaceans make up less than 6% of a polar bear’s diet, during the spring, close proximity with migrating whales in this strait can increase consumption rates with some individuals having more than half of their diet consisting of narwhal meat!!! (Galicia 2021) #2025MMM
Figure adapted from Galicia et al. 2021breaking down the amount of prey consumed by polar bears in various regions for both spring-summer (white) & fall-winter (gray). Some area show polar bears will eat a lot of narwhal, but other areas show no consumption of narwhal. Figure adapted from Galicia et al. 2021 showing a heat map of where polar bears consume greater amounts of Narwhal surrounding costal Nunavut, Canada. There is a very high density of narwhal consumption around the Barrow strait.
March 28, 2025 at 1:15 AM
tanisbp.bsky.social
Tonight begins in the high arctic, along the costal shore of The Barrow Strait in Nunavut. Here is where both arctic combatants call their native home, which they both have been enjoying with home habitat advantage through the first 2 rounds! #2025MMM
A map of the Barrow Strait and surrounding Canadian arctic archipelago from Richards et al. (2017). A thick red box highlights the strait along the coast of Devon island. Photo of the cost of Devon Island along the Barrow Strait. The image shows a steep shoreline of eroding sandstones devoid of large plants. A massive ice sheet makes curves from the background behind a rocky escarpment to the ocean, which sits calm in the foreground.
March 28, 2025 at 1:13 AM
tanisbp.bsky.social
Toothed whales (like Narwhal) have flexible rib cages that allow for lung compression in response to depth-related pressure changes that would otherwise cause their lungs to burst (Rommel et al. 2006). #2025MMM
A photo of an articulated narwhal skeleton suspended from above, the bones stand out against a black background. The skeleton is oriented as if swimming towards the camera, with the tusk entering the foreground. On the body is a prominent sternum with articulated ribs. Image Credit : Gunnar Creutz
March 28, 2025 at 1:11 AM
tanisbp.bsky.social
Polar Bears have high resting metabolic rates due to their large mass & carnivorous diet. They have adapted to prefer energy-dense prey to meet energetic demands & fuel daily activities (Pagano et al. 2018) & become "walking hibernators" in response to starvation (Lennox & Goodship 2008) #2025MMM
Figure adapted from Pagano et al. 2018 depicting a plot showing the relationship between body mass and resting metabolic rate comparing polar bears to other bears (& one sloth). The dashed line is the allometric regression for resting metabolic rate in vertebrate-eating carnivores, the solid line is the allometric regression for all eutherian mammals. Polar bears have a higher than expected metabolic rate for their body size compared to other mammals. An insert photo shows a polar bear in a metabolic chamber during testing.
March 28, 2025 at 1:09 AM
tanisbp.bsky.social
Last Up: 1-Seed POLAR BEAR (Ursus maritimus) vs. 2-Seed NARWHAL (Monodon monoceros). This battle was co-written with @chloejosefson.bsky.social & @mammalssuck.bsky.social‬ & me #TeamWork #2025MMM
Photo of a mother polar bear with two cubs standing among melting ice. The mother is standing in front of her cubs on all fours paused in motion, while the cubs are more stationary – half crouched and sitting. All three are staring at the camera. Watermark reads: “Carnivora – Ursidae, Ursus maritimus Polar bear. Image by LL Master, American Society of Mammalogists, Mammal Images Library Underwater photo of the head of a female narwhal descending into the deep across the camera’s axis. Without a tusk, the whale has a blunt, flat face which rounds into the body which turns a speckled blue on white.
March 28, 2025 at 1:08 AM
tanisbp.bsky.social
Sorry but I’m always on #TeamBones #2025MMM
Skull bones of a gar being held in the sunlight to see a long snoot filled with tiny teeth
March 28, 2025 at 12:10 AM
tanisbp.bsky.social
Narwhal tusks are very sensitive. Small pores filled with nerve endings allow Narwhal to sense changes in ocean salinity, which might allow them to find open channels of sea through melting ice floes. #2025MMM
Photo of a narwhal underwater in a deep blue world. The narwhal is swimming upside-down with its belly facing towards the camera. It’s long tusk is pointed upward and a clipart radar dish has been added to suggest the tusk is receiving information about the environment around it.
March 25, 2025 at 12:10 AM
tanisbp.bsky.social
Both mammals eventually need to find the surface to breathe. This can be dangerous because both species are incapable of breaking through sea ice! Instead they must find natural openings in the ice. #2025MMM
Photo of a large pod of narwhal all surfacing in the open water between large sheets of ice. The narwhal are all facing away from the camera and highly bunched together, many bumping each other in an effort to take a breath.
March 25, 2025 at 12:10 AM
tanisbp.bsky.social
While underwater the Narwhal spins around its axis & makes high frequency buzzing clicks. Tervo et al. (2021) hypothesized spinning widens the echolocation range to find prey. This comes with an energetic cost though, limiting dive durations. #2025MMM
Figure of narwhal dive profile adapted from Tervo et al. 2021. The different colors represent the three swimming modes (gliding, slow stroke, fast stroke). Smaller black dots represent buzz production and large-size markers indicate spins. A large purple box (added by me) highlights one such spin on the descent. Illustration of narwhal by Uko Gorter.
March 25, 2025 at 12:09 AM
tanisbp.bsky.social
Ribbon seals lungs evolved to squeeze down during deep dives, which have been recorded to go near 500m! Diving mammals rely on high amounts of iron-rich proteins in red blood cells & muscles to store oxygen during dives. Ribbon seals have more red blood cells than any other seals! #2025MMM
Graphs adapted from Lenfent et al. 1970 with bar plots show different oxygen storage in several marine mammals including ribbon seal, surrounded by purple box. Ribbon seals have very high oxygen storage per mass (top row) mostly thanks to very high oxygen storage in blood from hemoglobin and in muscles from myoglobin, highlighted with purple stars.
March 25, 2025 at 12:08 AM
tanisbp.bsky.social
On the other side of North America, the Ribbon seal just initiated a foraging dive of its own when it is suddenly whisked down alongside the Narwhal. Ribbon seals typically forage at depths of 200m, and the seal’s lungs quickly collapse under the water pressure! #2025MMM
Photograph from an aquarium of a ribbon seal swimming just below the surface of the water. The image was taken through glass so the seal is sideways, showing the striking contrast between black fur and wide white ribbons encircling the head, pectoral flippers, and hips.
March 25, 2025 at 12:07 AM
tanisbp.bsky.social
While both marine mammals call the icy waters of the North Arctic home, they actually don’t share habitats! Narwhal are typically found in the Greenland sea and Baffin bay, while Ribbon Seals live in the Bering sea. #2025MMM
Map of Narwhal distribution from Artic Portal.org with yellow highlighted areas depicting narwhal range surrounding the cost of Greenland up near Svalbard island. Map of Ribbon Seal distribution in light blue depicting their range existing around Alaska and the Kamchatka peninsula.
March 25, 2025 at 12:06 AM
tanisbp.bsky.social
Narwhal seasonally migrate >2,000km with changes to sea ice. Heide-Jørgensen (2002) found narwhal move together to the same locations year after year, & populations going to different areas have unique behaviors! #2025MMM
Photo from above looking down on a group of Narwhal all traveling together near the surface of the water. The group has males-with their big tusks, females, and some much small younger individuals. The individuals are all tightly bunched together.
March 25, 2025 at 12:05 AM
tanisbp.bsky.social
First Up: 7-Seed RIBBON SEAL (Histriophoca fasciata) vs. 2-Seed NARWHAL (Monodon monoceros) #2025MMM
Close up photo of a ribbon seals head, showing a dark fur covered face with big, black eyes and long vibrissae. The face is ringed by a white stripe. Near the back of the head is a box with a wire sticking out – a radio tag for scientists to track movements. Zoomed in photo of a narwhal head just above the water line facing the camera. The long, spiraled tusk is in the foreground and extends back into the face of the narwhal. The face where the tusk comes in is a dark blue, with obvious texturing of age on the skin. Moving away from the tusk the blue skin becomes speckled with increasing amounts of white blotches.
March 25, 2025 at 12:02 AM
tanisbp.bsky.social
Threatened by the approaching seal, the Tamandua rears up on its hind legs to better defend itself with long curved claws that can easily tear away at termite nests when foraging (Hayssen 2011). #2025MMM
Photo of a Tamandua among sparse grasses. It is sitting on its back legs, with its body upright and tall. Its arms are stretched outwards showing big claws, in a defensive "T-pose".
March 20, 2025 at 1:43 AM
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Ribbon Seals are typically less wary on ice than most seals, possibly due to poor vision in air (Boveng 2013). Craning his neck the seal tries to see if Tamandua is a seal pup. Pups are born white with a woolly coat of fur & only show markings when they molt at 3-5 weeks old. #2025MMM
Photo from above of an adult female ribbon seal to the right of a young pup. The adult seal is dark against the ice, with the classic ribbons running laterally around the neck and hip, and longitudinally around the flippers. The much smaller pup is completely covered in a thick coat of white fur called lanugo. Its dark eyes, nose and mouth are turned towards the adult. Image from Boveng et al. 2013.
March 20, 2025 at 1:41 AM
tanisbp.bsky.social
Tamandua spend very little time on the ground & this one clumsily walks around searching for trees, a stranger in a strange land....or lack of land. #2025MMM
Close-up photograph of the head and hands of the tamandua. The short cream-colored fur is visible along the arms and face. The face shows a long and slightly downcurved snoot, ending in a dark nose. The front legs are powerfully built but awkwardly holding the animal up with elbows splayed out. The hands are curved in so contact with the ground is made with the lateral surface of the hand, with long, sturdy claws tucked inward.
March 20, 2025 at 1:40 AM
tanisbp.bsky.social
Our battle takes place in the home habitat of the Ribbon Seal, on a thick ice floe in the Bearing Sea. Here a large male has hauled out of the water to allow for its annual molting of fur & skin. #2024MMM
Image from NOAA showing a ribbon seal on a small ice floe in a calm, icy ocean. The seal is facing the camera and has a dark black face with a thick white band around its neck. Two more wide, white bands encircle the sides of its body, around the pectoral flippers.
March 20, 2025 at 1:39 AM
tanisbp.bsky.social
Southern Tamandua are small arboreal anteaters with a long, thin nose. They are covered in pale cream fur with variable amounts of black patches around the shoulders, typically looking like they are wearing a vest or collar. #2025MMM
Photo of a tamandua on a branch facing the camera. Its long snout and face are covered in a golden cream colored fur. This fur covers the whole body in much the same coloration, except for a stripe running back from the shoulder to the back.
March 20, 2025 at 1:38 AM