Only on Twitter could a rodent pick a fight with the pope.
Earlier this month, Caplin, a 100-pound capybara, decided to speak up for his species.
"Stupid Pope said we are fish. ...How can capybaras legally be eaten at Lent? They're MEAT?," his Twitter account said. "Long ago Pope thought Venezuelans won't be Catholic if have to eat real fish so declared capybara fish. We hates that."
Melanie Typaldos, Caplin's owner (and Twitter typist), said her husband started their pet's Twitter account about a year ago. Caplin has more than 3,000 followers and uses Twitter to set the record straight on the capybara, the world's largest rodent.
Typaldos, a 54-year-old engineer from Buda, Texas, who has also written a book on capybaras, said she tweets whatever she thinks Caplin might be thinking. (And, incidentally, she added, "Capybaras do 'tweet.' They make a sound very much like a bird.")
"On Twitter, he's pretty upset because it's Lent now and the pope declared that people eat a lot of capybara," she said.
Caplin also sticks up for his smaller rodent brethren.
"He's rodent royalty and the protector of all rodents," she said. "He gets involved in conversations about rodents. Rodents are not really popular on Twitter. They do say mean things and he'll stand up for them."
In 140-character squawks, barks and chirps, pet lovers from around the world have taken on their animals' personas to talk, tease and even raise money for the animals they love.
"It's like a virtual version of what people do when they set up a play date with dogs or get together in the park," said Gregory Galant, founder of Sawhorse Media, which created Pet Feed, a dedicated Web site for "pets on Twitter."
When they launched the site last spring, he said, the site included hundreds of users. Now, he estimates that the number of pets on Twitter has grown tenfold. And it's not just your run-of-the-mill cats and dogs that tweet. Ferrets, fish, horses, turtles, rabbits, birds and, of course, capybaras, are all represented online.
Even online, animal rivalries die hard.
Matthew Schwartz, a 30-year-old lawyer from Arlington, Va., expected Twittering to come naturally to his flame-colored parrot Rudy.
"The messages were called 'tweets,' and I thought that would be such a perfect thing for a bird," he said.
With more than 1.5 million followers, Sockington is arguably Twitter's most popular animal. On a site that calls its messages "tweets," Schwartz (and Rudy) believe that's unfair.
"In those early days, Rudy spent much of his time lamenting the number of followers Sockington had amassed. At 20,000 Rudy called him the 'Wilt Chamberlain of cats.' At 50,000 he likened it to a virus that could soon reach the White House," Schwartz said.
In tweeted pleas to the Animal Planet's Twitter feed and letters to the editor of the New York Times, Schwartz has documented Rudy's mock campaign to unseat Sockington, which he calls "The Resistance."
Still, Schwartz acknowledged that the bird and cat have a "love hate relationship" on Twitter, since Rudy owes many of his followers to the "Sockington effect." In one day, he said, Rudy's account gained hundreds of followers after Sockington mentioned him in a tweet.
"Rudy isn't seeking fame; he's seeking sanity," Schwartz said. "If he can cause just a few people to realize the pointlessness of worshipping at the altar of Socks, he will be satisfied."
Most other pets on Twitter have humbler aspirations.
Christian Santiago, a 30-year-old New Yorker, said he and his wife started an account for their 5-year-old French bulldog as a joke.
"A few members of our family and friends had gotten to know Miss Piglet and wanted to see what she was up to," he said.
On Twitter, she ruminates about other dogs in the neighborhood, her favorite foods and, perhaps unfortunately, her bodily functions.
"i got a taste of freedom this weekend and loved it. what is up with this leash business anyway?!?," said one post.
"hmmmmmm, rawhides make my poops smaller," said another.
A number of pets on Twitter are using their social media connections to raise cash for animals in need.
Once a month, animal lovers around the world gather online for a round-the-clock virtual "PawPawty" to raise money for animal charities. Posing as their pets, people exchange messages and pictures on Twitter with other animal tweeters, using the hashtag #pawpawty to indicate their "attendance."
An official DJ tweets out a link to an online playlist so that all party animals can listen to the same song while they're on the Internet, and a security dog even monitors the party to help newcomers and keep spammers away.
Each month, a different charity and theme are chosen. and attendees are encouraged to contribute any amount to the featured charity while the 24-hour party rages around the world.
Since its first PawPawty last March, the "anipals" have raised more than $25,000 for philanthropic groups all over the world.
"I had no idea it was going to get as big as it did or has," said Lynn Haigh, the lead PawPawty organizer. About 20 people took part in the first "pawty," she said, but now 300 to 400 people join the party over the 24 hours.
Haigh, a 44-year-old project manager near Oakham, U.K., said she organized the first party soon after joining Twitter as her Cairn terrier Dougal. This week, she could win a "Shorty Award," for best nonprofit on Twitter.
Tweeting as her 6-year-old Persian cat Romeo, Caroline Golon, 39, who works in public relations in Charlotte, N.C., has raised more than $35,000 for animal charities. Every month, she chooses a different charity and every other month partners with PawPawty.
She said the animal community online -- on Twitter and beyond -- is a welcoming, supportive group. Twitter efforts like hers and Haigh's put that passion to good use.
"They want to do something. They want to be a part of it but they don't know what to do exactly," she said. "This gives them an opportunity to jump on board and do something that means a lot to them."