Hello again. Welcome back to LuxeSci - a podcast to re-ignite your wonder by exploring the science behind luxury items. I’m your podcast host, Dr Lex, PhD, infectious disease expert and avid fan of a faux animal print clothing item. I’m joined by my co-host Dimos, or should I say Dr. Dimos, also a PhD, electrical engineer and I think someone who has never worn an animal print item. Animal prints of all kinds have long been a part of fashion, fading in and out of what’s current but never being wholly out of fashion. Personally, I think there’s always something classic about a chic leopard print and it can even be used as a neutral since it pairs with so many colors and even with other prints (leopard print and stripes, yes!). Fortunately, actual leopard skin is no longer used since leopard are endangered species.
Background
Leopards are members of the cat family Felidae, genus Panthera
While they have a wide range, including sub-Saharan Africa, western and central Asia, Southern Russia and through Southeast and East Asia, the are estimate to occupy only 25% of their original range
The fur of a leopard is marked with rosettes (rose-like markings on the fur) and unlike panthers, the rosettes do not contain a spot in the middle
Rosettes are circular in pattern for East African leopards and more square shaped in Southern African leopards and larger in Asian leopards
There is a unique rosette pattern for each leopard
The coloration of leopards also varies by habitat with cream to yellowish coloring in arid regions, to darker, gold in mountainous and forest habitats
Note - black panthers are actually leopards with a recessive allele that causes the black color
Fun fact - leopards can run up to 36 mph (58km/)
The oldest leopard fossils are recorded from Europe and are estimated to be 600000 years old
Given that the oldest fossil of leopards is 600000 years old, it’s not a stretch to think that humans have hunted leopards and used their skins for a really long time. In more recent Western history, the Greek God Dionysus was always depicted wearing leopard skins. In the Benin Empire in Africa, leopards were commonly used in carvings and sculpture and symbolized the power of the king. The Ashanti similarly used the leopard as a symbol of leadership and only the king was allowed to use a ceremonial leopard stool
In more recent fashion history, (from a great article by Culture Whisperer blog) Christian Dior and Lanvin were advocates for the print in the 1920s and in the 1940s we saw the first use of leopard print in lingerie. The 1950s saw an uptick of leopard print fur coats (unfortunately). In the 1960s we saw the first use of faux animal fur and Dianne Von Furstenburg introduced her iconic wrap dress in 1974 with leopard print being one of the options.
The 80s didn’t see has much leopard but the print came roaring back with Azzedine Alias’ 1991 collection and there it has stayed since.
Research
So how do leopards get their spots?
Interestingly, it was mathematical super genius Alan Turing who first came up with the equation to explain how chemical reactions produce patterns in mammals (including leopard spots).
Turing noticed that when a leopard is born, the skin contains pigment cells that secrete chemicals called morphogens. These are thought to diffuse out of the pigment cells and react to produce color (mostly black-brown or yellow-red)
Research published in Physical Review E and highlighted on livescience.com showcased how this basic equation has been adapted to determine how the markings change from simple spots when leopards are young to rosettes in the adults
Morphogens - signaling molecules that act over long distances to induce responses in cells. Responses are based on the concentration of morphogen that the cells interact with
The researchers, Sy-Sang Liaw et al from Oxford University’s Mathematical Institute created a complex computer model to mimic the chemicals diffusion through leopard growth. They found that the concentration of the diffusing chemicals in the skin determines the exact markings of an adult leopard.
So for all of us (including me) who wondered what complex mathematical equations are good for in real life, this is great example of how math really does govern everything, even if you’re not necessarily working equations to determine why your calico cat is more brown than black
But what governs the deposition of the morphogens in the skin of leopard. The answer could lie with the common house cat and how their markings arise
To examine feline pattern development, a group out of Stanford University (Christopher Kaelin et al) used cats to explore the development of patterns on members of the cat family. (this study was published in Nature Communications in Sept. 2021)
Previous research has showed that in mammalian skin and hair, melanocytes are uniformly distributed during development and that the type and amount of melanin eventually produced by those cells is based in signaling in individual hair follicles.
Melanocyte - cell that produces melanin (found in the bottom layer of the skin epidermis and uvea of the eye)
Melanin - dark pigment primarily responsible for skin color
The cells in the skin and hair follicles continually produce the same type and amount of melanin throughout life so that the pattern grows along with the mammal
Kaelin et al define the stages of pattern definition in felines as follows:
Establishment of pattern element identify in fetal developments
Implementation of pattern morphology (shape) by signaling in hair follicles
Maintenance of pattern identity and morphology during growth
What Kaelin et al set out to do is to look deeper into what drives the development of pattern in fetal cats as a model of pattern development in the Felidae family (which includes leopards)
The group took fetal cat skin (sorry animal lovers though they were recovered from spay.neutering operations of feral cats in animal clinics) and used single-cell gene expression to track what genes and pathways were involved in development of patterns (specifically of tabby cats)
The team discovered that some of our favorite signaling molecules are involved in the process of deciding what the patterns in cats will look like.
The process starts very early in development where Dkk4-expressing keratinocytes (skin cells) decide early which skin cells will become lighter or darker
Dkk4 - part of the Wnt signaling pathway. We’ve seen Wnt signaling before in the episode on Cashmere. Now you may be tempted to think that Wnt signaling is somehow linked just to luxury goods (cashmere, leopard, etc) but remember that correlation does not equal causation. In this case, the Wnts are very common signaling molecules that are involved in many biological processes that span species
The take- away: genetics are heavily involved in the markings of the family Felidae and it happens very early in life and is set for entirety of the cat’s life. This may seem obvious but this is not how colorings and markings work for all animals. For example, in fish additional pattern elements can development as the fish grow and in cephalopods (octopi, etc), they have pigment cells that can change and flux depending on stimuli
Environment
So leopards are threatened species. This was initially because of over-hunting either due to the market for the fur or because they are predators who will take advantage of agricultural animals being housed nearby
Now, most of the lost of the population is due to infringement of habitat
A study in 2019 by Tariq Mahmood et al published in PLoS One found a 69% range contraction for snow leopards in Central and South Asia.
This includes the loss of snow leopards in 408 protected areas in Asia
The authors indicate that the maps they generated could be used for rewilding projects that would seek to not only protect current leopard populations but also restoring lost populations
Fun science
So why do leopards have spots? A paper published in 2010 in Protocols of Biological Science by Allen et al examined the variation in camouflage patterns in felines. The team found that attributes of their markings (spots, stripes, etc) were related to the specific cats’ habitats, how much the cats were in trees (arboreality) and how nocturnal (or not) they were. Interestingly, they found that the camouflage shifts to adapt to ecology over a relatively short time.
Basically, leopards have spots to help them hunt. It may seem like the pattern stands out to our eyes but in their natural habitat they are very well camouflaged for their usual prey
And there is a scientific reason that we can see the pattern so well. In a study published in Fronteirs of Psychology in 2021 by Coss et al, the researchers examined the behavior of 213 infants exposed to jars with leopard rosettes and snake scales compared to geometric plaid (hey old friend!) and plain. The infants interacted more with the snake scale and leopard rosette jars compared to plaid or plain and gazed significantly longer at the snake and leopard jars as well. The authors hypothesized that the biological patterns (snake and leopard) might be indicative of visual processing known to be involved in snake recognition.
So maybe we can see these patterns so well because they represent danger to us and we’ve evolved to be able to spot them easily. That’s why, if you want to stand out, a good snake skin or leopard print is still the way to go
As a counterpoint, research published in 2018 in Evolutionary Psychology by Shabbir et al showed that non-threatening patterns that were repetitive elicited similar attention-grabbing properties in adults as animal patterns. Perhaps we’ve evolved to respond to repetitive patterns as a way to identify threats back when our main threats were animal in origin
In summary, leopards have spots to camouflage themselves while hunting. These spots are present from birth in the skin. The responsible cells are called melanocytes, which produced melanin. Complex signaling is involved in this melanin production. Though the spots change to rosettes as the leopard grows, the location of the spots never change.
Humans easily recognize and respond to leopard as an evolutionary adaptation to be able to see harm coming
Glossary
Melanocyte - mature, melanin-forming cell (usually in the skin)
Melanin - dark brown or black pigment occurring in hair, skin or iris of the eye
Morphology - branch of biology dealing with the form of living organisms and relationships between their structures
Morphogen - signaling molecules that act over long distances to induce responses in cells
signaling pathway - series of chemical reactions in which a group of molecules in a cell work together to control a cell function
Fun Cocktail Party Facts
Leopards can run up to 36 mph
The oldest leopard fossil is from Europe and is approximately 600000 years old
Leopards don’t actually change their spots - unlike other animals, leopard coloring doesn’t adapt or change
Valentines Day fun fact - your heart pumps around 2000 gallons of blood a day. That’s one busy organ!
I hope you’ve enjoyed exploring leopard print with me and Dimos and I hope you remember a little fact from this episode the next time you see leopard printl. Thanks for listening to this episode of LuxeSci. A very special thank you to my audio engineer and co-host, Dimos. Our theme music is Harlequin Moon by Burdy. If you have a correction, comment or suggestion for a topic, you can reach me at: drlex@luxesci.com. We’re on Twitter and Instagram at luxescipod and our website is luxesci.podcastpage.io. Please subscribe to the podcast, please leave a review and special request this week, if you like us, send a text right now to a friend who you think would also enjoy the show. See you again in 2 weeks!
Episode 9 - Leopard Print
Fun science
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