Nandina: A Berry Interesting Problem

Oh, nandina, nandina, you trouble my heart!  You are so beautiful all winter with your green foliage and bright red berries, but you are an invasive plant.  What is a good naturalist to do?

Nandina, AKA heavenly bamboo.

Invasive species (species = type of organism) are a problem in Tennessee, and in the rest of the world as well.  They are currently the #2 cause of extinction of other species, just after habitat destruction.   Invasive species are non-native organisms that grow like crazy and take over.  Non-native organisms are moved from one part of the world to another, mostly by humans.  This is usually not a problem, except that for some non-native species, the new habitat has none of their usual diseases and predators, and the habitat seems to fit just right.  In that case....they can take over and crowd out the habitat of other organisms.  Nandina is native in Asia - from Japan west to India.  It is a beloved plant there, also used in landscaping like we use it here. 

Poisonous beauty: these berries contain nandina seeds and cyanide!

In Tennessee, some of our most harmful invasives are bush honeysuckle and kudzu.  Bush honeysuckle uses up habitat for other plants.  Also, birds that nest in it are more likely to get eaten (not sure why).  Kudzu simply crowds out every living organism where it grows.  Nandina is not that bad!  It is usually only found growing wild near where humans have intentionally planted it.  The Tennessee organization that helps keep invasive plants under control (TN-EPPC)  wants more information about nandina in order to keep tabs on the problem.  If you are ever out hiking in the wild (not in a landscaped yard) and you see a nandina, TN-EPPC would like to know about it.  You can report an escaped nandina at the TN-EPPC website: http://www.tneppc.org/

A nandina draws your gaze from behind a sedimentary rock.

Biologists worry about invasive species because they cause the total number of species to decrease.  The loss of a species, or extinction, causes the loss of a participant in an ecosystem.  For example, when a bird species dies out, an ecosystem might lose a seed-disperser.  If honeybees died out, there would be way fewer pollinators and thus way fewer fruits and seeds.  If a type of beetle died out, we might lose a soil recycler. 

Nandina is guilty of taking up a tiny bit habitat that would otherwise be used by native species, though it doesn't appear extremely aggressive.  It has another problem, though.  Nandina berries contain a toxin called cyanide.  Birds in the US haven't figured out how to deal with the poison, and some cedar waxwing birds have died from eating lots of the berries.  The berries can be toxic to any other animal too, so don't eat them. (It probably takes a lot of berries to hurt a large animal such as a human...still...don't eat them.)

Back to the original question: what's a good naturalist to do?  That depends on who you ask.  Some will say to never plant nandinas.  Others say plant them but clip off the berries this time of year when birds start foraging.  Others say don't worry about it - eventually the other species will adapt and nandina will become another important part of our ecosystem.  The only problem with this last option is that adaptation takes hundreds to thousands of years, so we won't find out how nandinas mesh with our Middle Tenneessee ecosystem for a looooonnnngggg time!  What do you think we should do?

Black Crowned Night Herons in Lincoln Park

There is a surprising diversity of animal life in Lincoln Park, and that's not even counting the zoo animals.  The latest residents of the park are what appears to be dozens to several hundred nesting black crowned night herons.    The two lumps in this picture are black crowned night herons.  Don't see lumps?  There's one in the center and one left of center near the top.  Try squinting. (Another neat thing about the picture is the lack of overlap in the adjacent tree canopies - competition for light.)

Black Crowned Night Herons Nesting in Lincoln Park

During the day, night herons sleep and nuzzle and generally take it easy.  I'd love to show you a picture of how cute this is, but the area is fenced off, and I don't have a zoom lens.  Trust me - it's cute.  Imagine fat birds cuddling with their heads tucked into each others' feathers.  Here's a better picture from the Lincoln Park Zoo website.  As the birds sleep on their nests or on nearby branches, the wind is waving the branches around like mad.  I wonder what it feels like to have wild rocking be one's version of sitting still.  It must make standing on solid ground feel uncomfortable.

These night herons are nesting in Lincoln Park for the second year in a row.  According to a birdwatcher I met by the night herons who seemed to know everything, this population used to nest in a wetland southeast of Chicago that was destroyed.  Then they moved to an island near Lincoln Park, and last year they moved here - just south of the zoo along the main promenade.  The zoo and the park have erected fencing around the nests for two years now, cutting off the main thoroughfare in the park for several weeks.  Everyone seems to be happy to welcome the birds, and they are back despite the busy park traffic, bagpipe players, dogs, soccer matches and live music concerts.  It will be interesting to see if the new habitat allows their population to survive or diminish.  They have nested earlier due to the extremely mild winter. 

Night herons hunt at night, and they eat all sorts of small meat items - fish, frogs, birds, squirrels.  Given the number of squirrels, geese and ducks in the park, it may be a good thing to have a top predator around to help control populations of these other organisms.

Leopard, Contained

Today I watched a leopard pace in its tiny cage.  Male leopards are used to 30 square miles of home range, and this one was lucky to have 30 square yards.  This subspecies of leopard, the Amur leopard, is critically endangered in the wild, and the zoo is participating in a conservation program that likely helps to maintain biodiversity so the species doesn't go extinct.  Nevertheless, this leopard was pacing.  There was a clear path worn in the grass, and he was bored.

Amur Leopard, Panthera pardus orientalis.

Leopards are often confused with jaguars and cheetahs, but once you look carefully at their spots, you won't confuse them again.  Leopards have hollow spots, called rosettes.  Jaguars' rosettes have little black spots inside each one.  Cheetahs have solid spots.  Leopards are the largest and stockiest of the three, with large males tipping the scales at 200 pounds, though most are smaller.

Notice the empty rosettes that indicate this is a leopard, not a jaguar.

Leopards' biggest difference from other big cats is a behavioral characteristic.  They are generalist carnivores.  They will eat anything from the size of a dung beetle to a 2000 pound male eland, as long as it is in the Animal Kingdom.  They prefer prey in the 44 pound - 175 pound range, which is a bit disconcerting for a species with most of its members in the preferred prey size range.  Leopards could take humans for prey easily - their range overlaps with humans, they are well camouflaged, and they can hide around human settlements.  For some reason, leopards don't choose to take humans - they hunt all other animals preferentially.  A few leopards that were injured or sick have taken humans as prey in the past, and once they started, they kept doing it until they were killed.

As explained in a previous post, generalist predators tend to have more intellectual capacity than predators that don't have to make as many decisions or learn about as many different types of prey.  Leopards hunt alone, which means they are unlikely to evolve complex social interactions, which is likely cold comfort to their prey.  Leopards are definitely stronger than other big cats of similar size, and they have been observed hauling prey up to three times their weight high up into trees to save for a later meal.  This combination of strength and intelligence makes the leopard particularly awe-inducing to me. 

The highlight of our leopard-watching for the day was a dangerous game between the leopard and a squirrel, two smart-cookie generalist consumers.  The squirrel had found a prized piece of hot dog bun near the leopard cage and was trying to decide whether to eat it in place or carry it away to another location, a vegetarian version of the leopard's prey-stashing.  The leopard heard the leaves rustling around the squirrel, crouched, sighted the squirrel and pounced.  The leopard was denied its afternoon snack by only a thin wire fence.  The squirrel continued to appear to frolic in the leaves, rustling them unnecessarily along the edge of the cage for another minute or two before it left to gorge on simple carbs.  The leopard was as agitated as a house cat being teased with crinkly paper.  It struck me that the squirrel had learned the fence would hold and ignored the deadly but contained predator.  The leopard had not completely habituated to the fence and continued to respond to temptations on the other side.  It either hadn't learned the fence was immutable or its brain was so exquisitely tuned to the rustling prey sounds that there was no other possible behavioral response the leopard could offer at the moment.  If you have ever played with  house cat, it certainly seems that they are compelled to pounce on rustling things - perhaps it is the same with big cats.

Leopard focused on a squirrel just two feet away.

Zoos and Conservation

The Lincoln Park Zoo is on my daily walking route now.  It's free and open to the public, and I can power walk right through or linger and marvel, depending on how I'm feeling and what the animals are up to.  It's a small zoo, but the construction of several of the animals' enclosures allow for jarringly intimate observations of the animals.

The gorillas and chimpanzees, in particular, are housed in such well-designed pens that I find myself moved and astonished by them as has not occurred in other zoo experiences.  The floors are elevated so the monkeys eyes are level with mine and the high-quality non-distorting glass allows a 1" distance between my skin and theirs.  I can see subtle changes in facial expression, lines in the soles of their feet, and individual hairs between the fingers of grooming chimps. 

A chimp comforting another after she was refused food by a male.

The resemblance in anatomy, emotion and behavior to humans makes these animals more interesting to watch than any other in the zoo.  Their enclosure is interesting enough that they seem to feel comfortable exhibiting a variety of the complex behaviors I have read about in Jane Goodall's accounts.  They groom each other, ask for food, diffuse conflicts, climb, play and interact with their surroundings.  It is difficult not to assume one understands their motivations and behaviors, since they look so much like us.

I watched this chimp make a nest of burlap sacks, try it out several times, readjust the burlap then roll over and suck her toes.

After awe and utter fascination, the strongest sentiment I have when watching these creatures is how unfair it is that they are put on display in fancy prison cells.  They clearly have lesser environments than they would in the wild.  Their behaviors and free expression are constricted.  They are aware of the constant stream of eyes looking at them.  The big silverback gorillas protest their enclosure by sitting with their backs always to the glass.  The animals are not happy about being enclosed.  I always imagine some more powerful aliens coming to earth and capturing a few of us for their zoos at home.  We would be outraged.

And yet, there is some considerable benefit to animals in zoos from a conservation perspective.  Zoos create opportunities for the development of strong affection of humans for animals, making us care about their continued presence on earth.  We are more likely to push for the conservation of chimpanzee habitat after experiencing reverence for them in a zoo.  In the worst case scenario, zoos have been the last refuge for species that are almost extinct.  The black-footed ferret once existed solely in zoos and has been reintroduced into wild land.  Zoos also provide the means for maintenance of genetic biodiversity, by shipping sperm or arranging for matings, so that a species has a wider variety of genetic combinations, reducing the likelihood of extinction.

If it were up to me to decide to free all the animals in zoos or keep them, I would be strongly conflicted.  Clearly it unethical to keep socially complex animals in tiny, uninteresting enclosures.  As zoos expand and enrich their animals' habitats, the balance shifts more toward the value of zoos, especially since humans will apparently destroy all natural habitats without education and enforcement of the alternative.  Zoos are an imperfect solution, but it seems that at least some zoos are necessary in our current world.  I know I'm going to spend a lot of time in the ape house at our zoo while I'm in Chicago, but my amazement will always be tinged with pity.

Japanese Beetles Put their Thumbs on the Scales

The stability of any ecosystem depends on having a multitude of species playing different roles in that ecosystem.  Some are producers, some are decomposers, some are predators, and no one gets out of hand.  The predators don't take over because there are bigger predators, disease organisms, and competitors for food and other limiting factors. 

Invasive species are the newcomer species that upset the fine balance, altering ecosystems and even causing extinctions.  For example, entire food chains have collapsed in the Great Lakes due to the invasion and overgrowth of the zebra mussel.  The zebra mussel eats all available algae, and other species starve.

Invasive species arrive in many ways - sometimes by expanding their range but usually because they have been carried from one place to another by humans.  Our species of the day, the Japanese beetle (Popilla japonica) (picture), was accidentally brought into the United States from Japan as grubs in soil of ornamental plants.  The new species was detected in New Jersey in 1917 and quickly traced to a plant nursery in the area.

Because invasive species are new to an ecosystem, they are neighbors with other species to which they have not evolved.  That means their neighbors have not had a chance to adapt to eating the invasive species, or competing with it or infecting it.  That's how you end up with entire mountains covered in kudzu.  Or the entire eastern United States covered in Japanese beetles (range map), despite massive federal, state and private efforts to destroy this aggressive farm pest.

But even invasive species are fascinating.  Japanese beetles are beautiful, metallic beetles.  Also, they might just be the only insect capable of growing one body part at a time, according to Dr. Hans-Willi Honegger, an entomologist who also works on the farm.  Dr. H thinks they might be able to grow their jaws, which would make sense since they are such voracious feeders.  Japanese beetles' life cycles are also very interesting.  They emerge in late spring, feed like crazy on leaves of their favorite plants, mate and lay their eggs in the soil.  Most of the adults die off by late August, but the larvae are just starting to get busy.  They burrow in the upper layers of soil throughout the fall, eating roots and organic matter in the soil.  When the temperatures start to drop, the beetles burrow deeper and deeper to stay warm only to come back up when the spring thaw comes again.

On the farm, the beetles are just starting to emerge.  According to the farm owner, the beetles have gotten a little worse over the past few years as their range has expanded.  Now that they are here, they are probably already laying eggs here for next year, and their numbers may increase.  Once beetles establish themselves, they are really impossible to get rid of, but several strategies can help.  A soil drought during early larval stages can kill many larvae; parasitic wasps, worms or bacteria can be released into the area to help kill beetles; traps do attract beetles, but they don't seem to help the overall problem; and insecticides are of course used on non-organic farms.  A surefire way to control Japanese beetles would be to simply wait around long enough for evolution to take its course.  All those Japanese beetles are a great food source for any animal that could evolve to eat them.  Given the rate of evolution, we might only have to wait about 20,000 years for Japanese beetles to become a part of our balanced ecosystem.