[EDIT: now crossposted on the tumblr]
This is something I worked out a while ago...like, in the last two years? 2014ish maybe. Because I was reading yet another werefic based on hilariously inaccurate theories of grey wolf social structure*, and I decided to finally hammer out my headcanon for D.Gray-characters being wereshifters. (Also the biologically-enforced-gender-role dynamics, but I'm leaving out that part because it's kinky but ultimately pisses me off.)
Assuming some humans manifest some sort of magical spiritual totemic bond with animals of a specific extant species of carnivore, but instead of being able to wolfwhisper you instead turn into a wolf; limiting the species pool to commonly known (/culturally significant) charismatic animals in a few of the Carnivora families, because most people don't know or care about fossa or binturong**.
CHARACTER -- WERESHIFTER FORM
ALLEN WALKER -- wolfdog! white/silver, either red eyes or one-red-one-grey
wolfdogs are hella dangerous--wolves are fierce wild animals, but will avoid humans; dogs have millennia of careful breeding making sure they love people and generally won't attack them. wolfdogs have both wild and domesticated instincts mixed together, making them unpredictable. Crossbreeding domesticated predators with wild predators isn't a great idea if you want a safe family pet...
KANDA YUU -- leopard! black, blue eyes
people who work with big cats in the film industry say leopards are mean. also, they ambush prey from trees, then drag the carcass back up the tree to eat it.
LENALEE LEE -- cheetah! violet eyes
highly specialized and built for speed, sweet, hunt with siblings; I think the daughters stay with their mothers for a while after reaching adulthood?
LAVI BOOKMAN -- red fox! green eyes
(note: yes, I know his nickname is "rabbit." no, I do not think that animal fits his personality in any way, shape, or form.)
BOOKMAN -- silver fox! panda-like markings
(the silver fox is actually a kind of red fox, but the color is very different)
KOMUI LEE -- dog! dark brown I think, some kind of East Asian purebred
REEVER WENHAMM -- dingo! (yes, an actual dingo.)
dingos aren't super dangerous, but they're definitely not domesticated pooches, and it's a really bad idea to leave small children around them.
CROSS MARIAN -- lion! red mane
I have to admit this choice was 50% the hair, 50% the mental image of Cross lounging around surrounded by ladies and not doing any of the work.
ALMA KARMA -- dog! (darkish) brown? some kinda terrier mutt
MIRANDA LOTTO -- fennec fox? black or dark brown? dark grey?
ARYSTAR KRORY III -- wolf! black & white
(his personality would be totally different in the were form)
ELIADE -- snow leopard!
snow leopards have furry snowshoe paws and big floofy tails and are the only cat species with grey eyes. while the other members of the Panthera genus lie down while eating, snow leopards crouch like smaller cats do. (also, they're the prettiest. u_u)
NOISE MARIE -- black bear!
black bears generally eat berries and stuff and aren't very aggressive, but god help you if you get between a mother and her cub.
DAISYA BARRY -- coyote!
HOWARD LINK -- dog! yellowish or golden brown, purebred shepherd or shepherd mix, English or German breed?
I think of Link like a working dog, K-9 (or actual sheepherding or something), not a pampered pet or junkyard dog. Sitting up straight, ears at attention, overly serious look on his face...
MILLENNIUM EARL -- polar bear! because reasons.
polar bears are apex predators in every sense of the word: out on the ice, everything is fair game. they can and will hunt humans--you have to prove competence with a rifle if you want to study up in Svalbard. (also apparently they go bananas for mint-flavored toothpaste.)
ROAD KAMELOT -- lynx! Iberian?
TYKI MIKK -- jaguar!
they have one of the strongest bites in the animal kingdom--while most other big cats kill prey by strangling them, jaguars just bite straight through the skull. also, like tigers, they love the water.
SHERYL KAMELOT -- silver fox I think?
JASDERO & DEVIT -- hyenas! Devit a spotted hyena, Jasdero a "blond" brown hyena bc they're shaggy~
NEAH CAMPBELL -- coywolf!
wolves run in packs and stay away from urban areas; coyotes are solitary and looove scavenging around; coywolves run in packs...and they're everywhere in New England, big cities included.
MANA CAMPBELL/WALKER -- dog! some type of purebred, English breed? maybe a shepherd or retriever...
aaand I'm still on the fence for a lot of the other characters.
(I apologize in advance for the taxonomy geekery contained below.)
* "Alpha/Beta/Omega" happens when you capture a bunch of unrelated wolves and cram them into a small enclosure together for the sake of science and/or lulz: fights for dominance, lots of tension, etc. In the wild, a nuclear pack consists of mom, dad, and the kids, who eventually strike out on their own to find a mate and build their own pack-family. If there's enough food, multiple packs will glom together to take advantage of it.
** The order Carnivora neatly splits into two groups, one with cats in it, the other with dogs:
> family Nandiniidae, a single sp of African palm civet
> superfamily Feloidea contains families Prionodontidae (2 spp of Asiatic linsangs) and Felidae (cats!!! ♥ ♥ ♥)
> infraorder Viverroidea contains family Viverridae (34 spp of civets, genets, the binturong, and the African linsangs), and...
>> ...the superfamily Herpestoidea, containing Hyaenidae (3 spp of hyenas and 1 aardwolf, that screams really scarily but actually eats termites), Eupleridae (Madagascar! 6 spp of mongoose, 2 falanoucs, the fossa, and the Malagasy civet), and Herpestidae (29 spp of mongoose, 4 kusimanses, and the meerkat! who doesn't love meerkats.)
suborder Caniformia (including both the largest and the smallest extant carnivores, the southern elephant seal and the least weasel)
> family Canidae (dogs etc.!)
> infraorder Arctoidea contains family Ursidae (bears! the giant panda; the spectacled bear; the sloth bear, sun bear, Asian black bear, American black bear, brown bear, and polar bear--the hybrid of the latter two is called a pizzly, and one of them almost got a polar bear hunter arrested when they realized how much it looked like federally-protected grizzly), and...
>> ...superfamily Musteloidea, containing Ailuridae (the red panda), Mephitidae (12 spp of skunks and stink badgers), Procyonidae (3 spp of raccoon, 4 coatis, the ringtail and the cacomistle, 3 olingos and the olinguito, and the kinkajou), and Mustelidae (57(!!) spp of weasels, otters, badgers, minks, polecats, martens, ferrets, etc.; yes, this includes the ermine/stoat, the sable, the honey badger, and the wolverine. note that a lot of these go after much bigger prey. also, apparently the domesticated ferret is actually a type of polecat! The More You Know.)
>> ...superfamily Pinnipedia, containing Odobenidae (the walrus), Otariidae (15 spp of fur seals and sea lions--these are the ones that prop themselves up, clap, and bark), and Phocidae (18 spp of true seal, that flop around on land and growl instead of barking; includes elephant seals, monk seals, the penguin-eating leopard seal, the fluffy baby harp seal, and the seemingly delicious harbor seal that brings great white sharks to the shores of Massachusetts every summer)
so, as you can see, there's a lot more to this group than just kitties and puppies. although, speaking of kitties and puppies...
 Felidae! 39-41 spp; the biggest is the (Siberian) tiger, the smallest is the super-sweet rusty-spotted cat
> subfamily Pantherinae has most of the big cats:
>> 5 spp in Panthera, the lion, the tiger, the leopard, the jaguar, the fluffy little snow leopard;
>> and 2 spp in Neofelis, the clouded leopards (which can climb down trees headfirst and hang upside-down off branches using only their hind feet (and tail)! clouded leopards are really weird)
> subfamily Felinae is mostly littler cats:
>> 3 spp in Pardofelis, the marbled cat (small, really long floofy tails, also climb down headfirst), bay cat (small, a vivid reddish color), and Asian golden cat (mid-size);
>> 3 mid-size spp in Caracal, the caracal (big black-tufted ears), serval (big ears, short tail), and African golden cat;
>> 10 spp in Leopardus, the Pantanal cat (small, may or may not be a differently-colored subspecies of the colocolo), the actual colocolo, Pampas cat (small, may or may not be a differently-colored ssp of the colocolo), Andean mountain cat (small, nearly identical to the Pampas cat), Geoffroy's cat (small, stand up on their hind legs like meerkats), kodkod (tiny and cute), southern tigrina (small, nearly identical to the oncilla), oncilla (/tigrillo; nearly identical to the tigrina), ocelot (a.k.a. dwarf leopard; mid-size), and margay (/tree ocelot; small, also climb down headfirst; where most cats have six teats, margays only have two!);
>> 4 mid-size spp in Lynx, the Canada(/ian) lynx (very fluffy), Eurasian lynx (much bigger than the others), Iberian lynx (almost exclusively eat rabbit), and bobcat (unlike the others, doesn't stick to only one type of habitat);
>> 2 spp in Puma, the cougar (mountain lion etc.) and the jaguarundi (small, called 'eyra cat' when reddish);
>> 1 sp in Acinonyx, the cheetah;
>> 4 spp in Prionailurus, the leopard cat (a subspecies of which is the endangered Japanese Iriomote mountain cat; small), flat-headed cat (super little, short tail), rusty-spotted cat, and fishing cat (mid-size; not to be confused with 'fishercats,' in the weasel family);
>> 1 sp in Otocolobus, Pallas' cat (or 'manul'; small, super floofy, looks like an ewok);
>> and 4 spp in Felis, the jungle cat (/reed/swamp cat, mid-size), sand (dune) cat (super little; the only cat to prefer desert), the black-footed cat (super little, adorably fierce; sucks at climbing, and digs burrows in the sand instead), and wildcat (a subspecies of which is the domestic cat)
note: if a cat has spots, someone somewhere probably calls it a leopard something or other. this can get kind of annoying, considering how distantly related they all are from what we call the true leopard, Panthera pardus, which is actually most closely related to the lion.
 Canidae! 35-37 spp; the biggest is the grey wolf (or various breeds of domestic dog), the smallest is the fennec fox (...or, probably, various breeds of domestic dog)
> bat-eared fox
> raccoon dog (tanuki)
> true dogs: the golden jackal, the side-striped jackal, the black-backed jackal, the Ethiopian wolf, the African golden wolf, the red wolf, the coyote, and the many subspecies of grey wolf (including the dingo and the domestic dog); the dhole or Asian wild dog; the African wild/hunting/painted dog(/wolf) (which are really cool ♥); the short-eared dog; the crab-eating fox; the maned wolf; the bush dog; and the culpeo, Darwin's fox, South American grey fox, Pampas fox, Sechura fox, and hoary fox
> true foxes: the grey fox, island fox, and Cozumel fox; and the Arctic fox, red fox (+ silver fox), swift fox, kit fox, Corsac fox, Cape fox, pale fox, Bengal fox, Tibetan sand fox, Blanford's fox, Rüppel's fox, and fennec fox (which apparently purr like cats!)
 The Iberian lynx is perhaps the most endangered out of all the cat species (most of which are threatened in some way), primarily because the European rabbit population has crashed twice in the last several decades. The second time was a pandemic of rabbit hemorrhagic fever spread by domestic rabbits; domestic rabbits from Europe were imported to China in '83, the virus spread to local rabbits (probably mutating along the way), then spread back across the continent to Europe and beyond. The first time, though, can be blamed entirely on the actions of some asshole in France who wanted to exterminate the rabbits infesting his walled estate in a new and exciting way--so in 1952 he deliberately released the Myxoma virus within those walls, assuming there was no possible way it could get out, because rabbits definitely can't burrow under things like walls, and it's not like the disease had a known insect vector or anything, right? Yeah, within two years at least 90% of the wild rabbit population in France had been completely wiped out, and the virus spread outward from there. (Note that hares, jackrabbits, and cottontails--like the Eastern and New England cottontails--are totally unaffected by RHV, and aren't affected as severely by myxomatosis. Domesticated rabbits, unfortunately, are European rabbits, and their mortality rate from these two diseases makes Ebola look like a minor cold.) So, Iberian lynx conservation! Consists mostly of protecting their habitat, like with most species, but also vigilantly monitoring and managing local rabbit colonies.
 I'm serious, the manul is the weirdest-looking cat I've ever seen)