What is a keystone species?

A keystone species is any species that plays a critical role in how the ecosystem functions. Couldn't one argue that every species is a keystone species, playing an important role? Well, a keystone species plays a disproportionately large role in maintaining the ecosystem structure and function.

Sea otters are a great example of a keystone species

For example, let's look at sea otters. They're a common example of a keystone species. Why? Well, because they feed on urchins. Urchins feed on kelp. By preying on the urchin population, sea otters prevent urchins from consuming too much kelp. Kelp forests are home to many species, including invertebrates, fish, and marine mammals. In addition to being important habitat, lots of other animals feed in the kelp forests, such as seals and sea lions. Kelp forests can be destroyed by urchins, but the sea otters feed on urchins, preventing this from happening. Without the sea otters to feed on the urchin, the urchin might consume massive amounts of kelp, destroying important habitat feeding waters for other animals. So the effect of this one species on the ecosystem is very large, larger than one would expect for a single species.

Many predators function as keystone species, limiting the population growth of multiple omnivores/herbivores. Wolves eat deer and deer eat small trees, so wolves protect this new growth. Jaguars, tiger sharks, mountain lions and sea stars are all predators that function as keystone species.

Pacific salmon is another good example of a keystone species and not because of what this species does during its life but because its death is so important. The salmon life cycle involves salmon returning to the freshwater streams they were born in to spawn (males release sperm and females release ova into the water) and then die. Like anything that's dead, the salmon then decompose in these waters. Their death provides a significant amount of nitrogen to the watershed (the area of land where all of the rain or water under the land drains to, click here for more info).  Salmon runs, when salmon return to the freshwater they were born in and spawn themselves, provide a crucial source of nutrients to areas that otherwise might have low productivity, and they act as a food source for many animals, including grizzlies and eagles.

Red mangroves

But let's not forget our green friends. Plants can function as keystone species too. Red mangroves, Rhizophora mangle, are found at the edge of the water. Their roots act as a nursery to fish and crustaceans. Red mangroves provide habitat for many species, such as manatees, birds, and fish, They protect against erosion and act as buffers from large waves, literally structuring the land around them by preventing soil erosion and acting as anchors.

The concept of a keystone species was first introduced by Robert Paine in 1969, who studied sea stars and noticed that removing this key predator had cascading effects. Since Paine's work, we've come to realize the importance keystone species have in their communities. These important species are often targets for conservation efforts, as conserving them protects many species and ecosystems.

Food for thought: Do some research on the reintroduction of wolves to Yellowstone National Park. How did the arrival of wolves in 1995 change Yellowstone? How is this example of a keystone species connected to conservation in Yellowstone?

If you want to learn more, check out this great resource from Nature: Keystone Species.

Orangutan called a "Non-Human Person," one that can be freed Part II

Yesterday, I wrote a post about an orangutan in Argentina that was recently freed by the courts after being declared a "non-human person." I found this interesting for more than one reason, and I wanted to share the second one today.

In response to this ruling, the head of biology at the Buenos Aires Zoo stated, "When you don't know the biology of a species, to unjustifiably claim it suffers abuse, is stressed or depressed, is to make one of man's most common mistakes, which is to humanize animal behavior" (see article here)  and I think this is an excellent and often overlooked point! I can't speak for this zoo because I've never been and I don't know anyone who has been. I can speak to my experiences at the Smithsonian National Zoo where I interned for several months as an undergrad.

Orangutan named Kiko crossing the O-Line at NZ

I would often hear guests complaining that the gorillas were just sitting there. "Why aren't they doing anything?!" Well, when you consider that gorillas are large herbivorous animals that spend much of the day foraging on leaves and another significant portion of the day resting and digesting those leaves, it makes sense that they're not always climbing trees and playing. Most primates spend very little time playing in the wild. I know the primates at National were extremely well cared for. They have enrichment time to keep them from getting bored, they have keepers who really care about them and have worked there for years, and they eat better than most humans do. Should apes be kept in zoos? Well, that's a hard question to answer.

I don't believe apes should be kept as pets or in the entertainment industry. They're not for our entertainment purposes and the idea of keeping a highly intelligent, huge, and strong animal in a home is absurd. Remember Charla Nash? Keeping apes in zoos may or may not be different though.

Zoos allow people to see and hopefully learn about many different types of animals they otherwise might never really learn about unless they can afford to travel. Watching a television program isn't the same as seeing a zebra in a zoo which isn't the same as seeing one in the wild. I saw a lot of children's eyes open wide when running up to see the gorillas feeding outside or the orangutans crossing on the O-Line, a series of long ropes and towers (electrified at the base so they won't want to climb down). Click here for a video of orangutans using the O-Line. I'd like to think these children (and adults) really enjoyed their time at the zoo but also learned a thing or too, including an appreciation for nature and wildlife. There's something magical about seeing an animal in the flesh.

Brown bear at National Zoo-Thankfully exhibits have improved greatly.
Historic Images of the Smithsonian

Now,  not all zoos are created equally. Some animals do live in very small confined spaces or receive inadequate care. I don't think large animals such as orcas should be kept in captivity at all. Just watch the movie Blackfish if you haven't already. That said, animals in zoos do tend to live longer than those in the wild. They receive medical care and lots of healthy food. They're also studied in a way that may not be possible in the wild. We know their lineages, we know exactly what they eat, we can watch them 24/7, and we can use cognitive tests as enrichment to understand their brains. There are definitely advantages to having zoos. Some zoos are centers of genetic or cognitive research. A few zoos even have excellent conservation science programs, funding scientists who study wild animals and initiatives that support the protection of wild animals and ecosystems.

Do these advantages outweigh the disadvantages of keeping animals in captivity? I'm undecided. Most zoos are aware of the problems they face. They want larger exhibits for their animals. They're trending towards creating the most natural environment possible. I hope this work continues and I hope zoos do more to ensure that visitors are actually learning when they come to the zoo. Do you stop and read the signs telling you all about a species or an issue? I'm not sure many people do, but creating more interactive displays, having keeper talks, and using technology may make the visit memorable and change perceptions. If the focus is on educating the public, conservation, and raising awareness about issues rather than making money, then zoos might be worth it.

Orangutan called a "Non-Human Person," one that can be freed Part I**updated

A case in Argentina is making headline news around the world.** An orangutan (an ape, just like humans are apes) has been ruled a "non-human person" that deserves corresponding, basic rights. The Association of Officials and Lawyers for Animal Rights successfully argued that Sandra, an orangutan born in captivity and currently housed at the Buenos Aires Zoo in Argentina, deserved freedom from the confinement she currently experiences.

I think this is an interesting story for a couple of reasons. For starters, the court did NOT rule that Sandra deserved the same rights as a human. The wording specifically states that she is a "non-human person." Now, what does that mean? Great question. It'll be interesting to see how this story develops. Humans, orangutans, gorillas, chimpanzees, bonobos, gibbons, and siamangs are all apes. Apes are characterized by larger brains than other primates and lack of a tail. We're more closely related to other apes than we are to lemurs or monkeys, but we're certainly a different species than our close relatives. We last shared a common ancestor with orangutans about 16 million years ago, meaning that orangutans and humans have been on separate evolutionary paths for this amount of time. That's a decent amount of time, and obviously a lot of differences have occurred since then. The phylogenetic tree, which represents the relationship between different species, shown below may help you visualize the relationship between different apes. Humans and chimpanzees last shared a common ancestor roughly 6-7 million years ago. We last shared a common ancestor with gorillas around 9 million years ago.

Tree showing the amount of time passed since humans split off from different apes. Humans are more closely related to chimpanzees than to gorillas. For more on how to understand phylogenetic trees, click here.

I do not think non-human apes should be awarded the same status as humans. However, I think awarding apes some rights may be a good idea but may also have unintended consequences. I am an advocate for animal rights in general, believing that it is our responsibility as intelligent humans to make sure that no animal is treated cruelly. Many primates live in complex social groups, they certainly display different emotions, and some even are capable of simple language. Regardless, non-human apes are not the same as humans. Before we brashly declare that they deserve to be considered the same as humans, we need to think about the potential consequences of those actions.

Primates are often used in biomedical research. Many believe primates should not be used this way (check out this link), but there are still those who believe we need to continue (read what proponents for primates in biomedical research have to say). The argument often used to continue primate biomedical research is that the number of primates used in research is very small and the number of humans helped is often very large. Whatever side of the line you stand on, declaring primates or just apes separate rights from humans will likely have a cascading effect on primates used in medicine.

I recommend listening to both sides of the debate on using primates for biomedical research before jumping to any conclusions. I'm a firm believer that there's no such thing as too much research so do your own on this issue! That said, I like that this orangutan was pointedly not declared a human. The zoo has time to appeal the court's ruling, which I would guess they will do. It'll be interesting to see how this case of non-human personhood plays out.

Tomorrow, I'll talk about apes in zoos and an important point an official of the Buenos Aires Zoo makes.

**The Nonhuman Rights Project obtained and translated the original court ruling and determined that the media got much of it wrong concerning this case. Nowhere did the court explicitly state that this orangutan nor any animal is entitled to rights and habeas corpus was not granted. Read more here.


Additional reading/links:

Non-human primates: the appropriate subjects of biomedical research?

 Primate tree

How human are chimps?

Should apes have rights?

How human are chimps? The differences and similarities between chimpanzees and humans.

The state of New York recently ruled that chimpanzees are not entitled to the same privileges and rights as humans. Chimpanzees have long given humans plenty to think about when it comes to defining what exactly is human. Jane Goodall, when she observed chimpanzees using tools in the wild stated, "Now we must redefine tool, redefine Man, or accept chimpanzees as humans." I decided to look at some of the ways chimps are just like us and some of the ways they're not at all like humans.

Young chimpanzee. Photo credit Sabine Bresser

Like humans:

1. Chimps taken from their mother at a young age suffer long-lasting behavioral consequences. Specifically, chimps raised by humans rather than other chimps groom each other less frequently than chimps raised by their chimpanzee mothers, and they also engage in sexual behaviors less frequently. Read the study done by Freeman and Ross at the Lincoln Park Zoo here. Looks like each species should probably raise its own young.

2. Chimps can cooperate and do so spontaneously. In a study where chimpanzees were given access to a task in a larger outdoor area, as opposed to a small, controlled area where most testing typically occurs, chimpanzees had the choice to use the apparatus and try the task or avoid it entirely. Surprise! Chimpanzees chose to use the apparatus, which required cooperation and choosing a partner chimpanzee to achieve the task, meaning chimps don't just work together when there's nothing better to do. These chimps sought cooperation out. Check out the article by Suchak and others here.

3. Chimps display different cultures, as shown by separate populations of chimpanzees using tools in different ways despite seemingly the same ecological conditions. A 2010 study examined how two populations obtain honey (a real treat for a chimpanzee) and found one population using sticks while another used wedges of leaves to soak up the delicious and highly coveted food item.

Unlike humans:

Photo credit Sergio Morchon

1. Chimpanzees may be able to communicate, but they have yet to display a mastering of complex language and grammar. While yes, chimps and other apes have a grasp of sign language and some even use computers and symbols to communicate with humans, are they capable of knowing the difference between sentences such as, "I bit the dog" and "The dog bit me?" The answer appears to be no. For a great film that I highly recommend, watch Project Nim. It's thought-provoking, heartbreaking, informative, and definitely worth a watch if you're interested in language or even more broadly interested in chimps.

2. Chimpanzees don't teach their young. Now, this might be a somewhat controversial claim since teaching in animals is hard to study (how do you determine if one it is one individual's intent to share knowledge with another?). Chimps certainly learn by watching other chimps and new behaviors are socially transmitted, but does one chimpanzee purposefully and knowingly teach another? Even if you disagree with me, you must admit that humans take teaching to a new level. With our creation of schools and our ability to guide and help others in a hands-on way, we take teaching to a level definitely not seen in chimps.

3. Finally, chimpanzees are not nearly as adaptive as humans when it comes to geography. Homo sapiens, or humans as we know and love ourselves today, weren't even the first to leave Africa and travel to other continents. Our earlier humans ancestors did that first, but the fact remains, humans love to travel. We have blogs dedicated to traveling, the desire to know what's just over that mountain or on the other side of the lake. We seemingly need to go everywhere and we're on every continent if you include the research done in Antarctica. We've adapted to all of these different climates through tools and clothing and behavioral adaptations. I don't think anyone can argue chimps have caught the travel bug quite like humans have.

Food for thought: Does learning these facts about chimps change the way you view what it means to be human? What is the most important difference between chimps and humans? What is the most important similarity?