Rare sharks, toads, rhinos and bears are among the endangered species in the news this week.

Hammer Time: David Shiffman offers 10 reasons why great and scalloped hammerhead sharks (Sphyrna mokarran and S. lewini) deserve Endangered Species Act protections and encourages people to take direct action in support of a move to do just that. As Shiffman reminds us, online petitions don't do any good, but submitting a public comment to proposed rules can make a difference.

Success in Texas: Thousands of Houston toad (Bufo houstonensis) tadpoles were released into Bastrop State Park this week in an effort to keep the species from going extinct in the wild. The tadpoles, all spawned at Houston Zoo, will supplement the wild population which was devastated by wildfires in 2011. Their future in the wild is iffy, though, since most of Texas is privately owned and many people don't want endangered species on their properties.

I Don't Understand. It's hard enough to arrest rhino-horn smugglers, let alone prosecute them. Language barriers make it harder still. South Africa recently released two Vietnamese men accused of smuggling rhino horns because the courts could not find anyone to serve as translators. The men, who were caught carrying 12 rhino horns hidden in their luggage, actually sat in jail for 30 months before being released, but they could have faced an additional 10 years in prison if convicted.

What do Endangered Species and Child Pornography Have in Common? Both are traded deep in the hidden "dark web" of the internet, the same secret pockets—inaccessible through Google—that also support a gun-running, drug trafficking and a wide range of illegal activity.

Mongolia Needs You: Mongolia's former Minister for Nature, Environment and Tourism has issued a powerful plea to the international community to help save the critically endangered Gobi bear (Ursus arctos gobiensis), which he says is ignored in favor of species like the giant panda. "This animal, given its population drop and ever-worsening habitat, is arguably now facing the final seconds of its countdown to extinction," he writes. For more information on this rare subspecies, read my article from last year about the last 22 Gobi bears.

Celebrity Plea of the Week: Musicians from Def Leppard, Deep Purple, Guns N' Roses and other hard-rocking bands are calling for an end to bear bile farming in Asia. Bears in China and Vietnam are "milked" for the bile in their gall bladders, which are used in traditional Asian medicine to "treat" all kinds of ailments. You can read my articles about bear bile here and here and watch the "Can't Bear it" PSA below:

Well, that's it for this time around. For more endangered species news stories throughout the week, read the regular Extinction Countdown articles here at Scientific American, "like" Extinction Countdown on Facebook, or follow me on Twitter.

Photo: Great hammerhead shark by Wendell Reed. Used under Creative Commons license