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Is Being A Black Panther Beneficial? It Depends.

2019-12-18 23:33| 发布者: hujian| 查看: 74| 评论: 0

摘要:   Black cats have long intrigued us, from comic book heroes to symbols of superstition. They’re also more common that you might think: At least 14 of the 35-plus species of wildcat—including jagua ...

 


 Black cats have long intrigued us, from comic book heroes to symbols of superstition. They’re also more common that you might think: At least 14 of the 35-plus species of wildcat—including jaguars, leopards, and bobcats—can carry a gene that causes melanism, or a surplus of melanin, or pigment, in the cat’s fur. The term “black panther,” in fact, is a catch-all term that refers to any wildcat with a black coat.

  The persistence of melanism among wild felids suggests it offers some advantage, such as camouflage or regulating body temperature.

  Now, new research published December 18 in the journal PLOS ONE has unearthed a potential downside: Hindering communication. Many wildcat species possess white marks on the backs of their ears and tail tips that allow them to signal crucial information to other individuals—markings that don’t exist in melanistic cats.

  For the study, ecologist Maurício Graipel of the Universidade Federal de Santa Catarina and colleagues modeled the connection between black coats and communication. Their results suggest that though better nighttime camouflage is a boon of being a black cat, the absence of white markings is their Achilles’ heel, resulting in an evolutionary dilemma—is it better to be melanistic or not? (See our exclusive picture of a rare black wildcat seen in Africa.)

FollowPhotosSTUNNING PICTURES OF BIG CATSloading...
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  Lions are threatened throughout most of their African range. But nowhere is their condition as perilous as in Kenyan Maasailand, where this large male was photographed. Lions there, which number fewer than 150, are under imminent threat of extinction from Maasai herdsmen thought to be retaliating against prides who prey on their cattle.

  PHOTOGRAPH BY JOHN EASTCOTT AND YVA MOMATIUK

  There’s no clear answer, but the research is a compelling look at such tradeoffs, which are the hallmarks of evolution, says Nicholas Pilfold, a scientist in population sustainability at the San Diego Zoo who contributed to the scientific confirmation of a black leopard in Africa earlier this year.

  “Often, we focus on the adaptive advantage of a particular trait and ignore the cost,” says Pilfold, who was not involved in the new study. “The strength of this study is that it suggests a cost that may influence how melanistic cats behave and under what conditions the trait may persist.”

  What’s more, understanding more about melanistic cats may help protect the animals, many of which are declining due to habitat loss and poaching. At least 18 wildcat species are either endangered or vulnerable to extinction, according to the International Union for Conservation of Nature.

The ears have it

  Graipel was investigating the activity patterns of the southern tigrina (Leopardus guttulus), a house cat-size feline, in southern Brazil, when his camera traps captured evidence of both melanistic and non-melanistic animals.

  To his surprise, the data showed that melanistic tigrinas were more active during moonlit nights than the regularly spotted tigrinas. Graipel and his colleagues attributed this pattern to the black cats’ more effective camouflage, which renders them less visible to both predators and prey.

[video]https://www.youtube.com/embed/Y80YG9EBGxQ[/video]

  However, Graipel noticed something else: While non-melanistic tigrinas have white spots behind their ears, their melanistic cousins are missing these bright spots of fur.

  White is conspicuous at night, and all cat species are at least partially active in the dark, Graipel wondered about the role of these white marks in visual communication—and what it would mean for the melanistic cats that lack them.

  So Graipel and his team collected records of all the scientifically confirmed occurrences of melanism in the cat family that they could find. Then they scoured books, articles, and the internet for images of cats with white marks on the backs of their ears. To this data, they factored in ecological characteristics of the species, such as their activity levels during day and night, and used statistical modeling to investigate the association between black coats and communication.

  “Considering that positioning of the ears can signify many things, especially to other individuals of the same species, and that felines are able to see very well even in low light, such white marks can serve as a silent warning signal to those following them at night,” Graipel said in an email.

  In addition, mother cats can warn their kittens of danger ahead by raising their heads and stretching their ears, flashing their white spots, he says.

Lucky black cats?

  The vital role that white markings play in cat communication may limit the number of melanistic individuals in most cat species. However, if a species is active during the day, then having a dark coat may not be so bad.

  Take South America’s jaguarundi, for example. It’s the most day-dwelling wildcat, so nocturnal communication by white marks is less important for survival. Supporting that theory, about 80 per cent of jaguarundis are melanistic, the highest frequency of melanism among all cat species, Graipel says.

FollowVideoRemote Cameras Confirm Rare Black Leopards Living In KenyaFebruary 12, 2019 - San Diego Zoo Global researchers have confirmed the presence of rare black leopards living in Laikipia County, Kenya.loading...

  FOOTAGE PROVIDER: SAN DIEGO ZOO

  SOURCE: DA SILVA AND OTHERS, "MAPPING BLACK PANTHERS: MACROECOLOGICAL MODELLING OF MELANISM IN LEOPARDS (PANTHERA PARDUS)," PLOS ONE, 2017

  Even within species’ populations, the frequency of melanism can vary. This is the case for leopards, which range across Africa and Asia. Melanistic leopards living in the open savannas of Africa, where the cats hunt both night and day, are extremely rare. But in the dense forests of Malaysia, where leopards are mainly active during the day, rates of melanism climb to 50 per cent of the population. According to Pilfold, the new findings provide context to why these differences exist between populations.

  “A better understanding of how habitat use may be influenced by the presence of melanism in a population,” he says, “can help us ensure that the appropriate habitats are protected to conserve these species and their unique traits.”

  Follow Mary Bates on Twitter.

Lead Image: A black jaguar swims in Brazil. The term "black panther" is an umbrella term that refers to the 14 species of wildcat that can have melanism.

  PHOTOGRAPH BY FRANS LANTING, NAT GEO IMAGE COLLECTION



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