The Invader

Florida has the distinction of being the epicenter of invasion of non-native reptiles, introduced by collectors who intentionally or unintentionally let non-natives escape, or by accident when eggs or small hatchling reptiles are carried into this country on imported plants.

The Cuban Brown Anole is a 5-9 inch slim lizard, marked with a diamond-shaped pattern on its back. It typically rests in low vegetation, waiting for unsuspecting insects — or other, smaller lizards — to walk by, and then quickly gobbles them up.

Successive invasions of Brown Anoles from Cuba and the Bahamas since the late 1800s have resulted in well established populations throughout Florida that have since moved north and west to Georgia, Louisiana, and Texas, and have also resulted in an apparent coincident decrease in the population of native Green Anoles.

Brown Anoles now occupy the tree trunk-ground niche in their hunt for prey, and occur in very high density in residential shrubbery (sometimes 4-6 to a single bush).

Female Brown Anoles (recognized by the brown stripe down the middle of their back) lay 1-2 eggs in leaf litter or potted plants every few days. Eggs hatch 4-6 weeks later, and the 1-inch long hatchlings move into the vegetation to hide from larger individuals that might eat them.

However, rather than disappearing altogether as a result of the Brown Anole invasion, it may be that Green Anoles simply move out of the low vegetation and up into the tree tops where they can more favorably compete for food and avoid being eaten by the more aggressive Brown Anole.

An unwanted invader

The European Hare is one of the most widespread mammals on earth, due not only to its ability to thrive and reproduce in a wide variety of habitats, but also to its intentional introduction to new geographical areas by humans.

We saw this European hare in a small farming community on the shore of Lake Titicaca, Peru.

For example, 36 hares were intentionally released in central Argentina in 1888 and just 20 years later, they were so widespread in Argentina, they were considered a major agricultural pest. Another intentional release of hares in southern Chile in 1896 may be the source of animals that have subsequently invaded Bolivia, and more recently, the southern tip of Peru, where they were first discovered as recently as 2002.

A dozen or so hares scampered through the brushy fields intermixed with small crops, fleeing as soon as they saw us.

The mixed grassy field-small crop production areas, broken up by thickets and stone walls are perfect for this little invader, which seems to do well from sea level to high altitude zones.  The only barrier to its rather rapid rate of dispersal in South America so far is the humid and complex tropical Amazon region and densely populated urban areas.

It’s brown, tan, black and white blotchy fur pattern blends well with rocky areas of the same color, giving the hare some ability hide in plain sight.

The spread of European hares in these small farming communities where plowing, planting, and harvesting is all done by hand on small plots would have a great impact on farmers’ yields.

Mixed vegetable crops on the shore of lake Titicaca are ripe for harvest by fast multiplying European hares.

In Argentina, hares are a favorite prey of Puma (cougar), but top cat predators are absent in this area of Lake Titicaca.  It’s possible that avian predators in this area might take young hares, but adults are large, long-legged, fast runners with great endurance for escaping predators.

Run, rabbit, run…

So for now, the European hare has an open niche to exploit, from coastal to high altiplano farms and fields in Peru.

color me beautiful

The Amur Maple forest has once again reached its full fall splendor.

The introduced Amur Maple is really more of a tall shrub, but it grows so densely along the roadside it forms an almost impenetrable forest.

Dense thickets of Amur Maple crowd out and shade out natives that might grow there —  really the only thing this species has going for it (in my opinion) is the brilliant color display of its fall leaves.  The ground cover beneath the trees looks like a collection of fallen leaves, but on closer inspection, it seems to be a mini-forest of Amur Maple seedlings, ready to bolt up as soon as a light gap appears in the forest overhead.

Bare branches above, lots of colorful leaves on the ground — right?

There are some fallen leaves here, but there are more tiny seedlings, each with just a few leaves, carpeting the ground and leaving no bare areas for anything else to invade.

It’s a very photogenic forest, and easy to walk through since there is no understory.

The birch in the background established itself first here, but the Amur Maple seedlings beneath the birch will make it impossible for birch seedlings to get established.

but what color!

Another glorious Indian Summer day

the Amur Maple forest

Its leaves turn a brilliant red and gold in the fall and it grows in dense, moderate-height thickets along road sides and walkways, making it a favorite landscaping plant.

But Amur Maple is a rapid spreading, highly invasive tree that can quickly establish itself, shading out perennial forbs and grasses, as well as saplings of native tree species. Its prolific seed crop and rapid growth allow it to get established wherever there is enough light and moist soil.

Amur Maple saplings (probably offspring of the trees that line the walking path) growing in a field of goldenrod. Eventually the height of the trees will shade out the perennial plants in this old field.

Under the right environmental conditions (adequate light and soil moisture), Amur Maple can grow 3-4 feet each growing season, allowing it to take over an open field like this one.

Originally native to northeastern Asia (eastern Mongolia to Korea and Japan), the Amur Maple is tolerant of extreme cold, making it a good candidate for boulevard trees in northern climates like Minnesota and northern Europe.

They may be thought of as “weed trees”, but they certainly enhance the fall landscape.

The Robin in Winter…or why Robins don’t migrate

Their scientific name (Turdus migratorius) suggests that Robins are only temporary inhabitants of this harsh northland, and indeed, it would seem to be a bad idea for a fruit and insect specialist to stick around here during the coldest weather when plants and insects are inactive.

We are used to thinking of Robins as harbingers of spring, migrating back only when the ground thaws and the earthworms become active, but some Robins are hearty and savvy enough to remain here all winter, even during the coldest, and snowiest weather.

The overwintering, non-migratory Robin — see my earlier post in December 2013.

So, how do they manage to stay warm, find enough food they like, and tolerate these harsh conditions?  (On a day like today, with 40 mph winds chilling the already subzero air, I have to wonder how anything tolerates living here.)

Maybe eating fruit isn’t such a bad strategy for a bird that overwinters in northern latitudes.  Consider the advantages:

1) fruit is full of sugar, and some fruits have a waxy coating that is digestible, providing extra calories;

2) when you find a tree or bush with fruit, there is usually a lot of it, and a bird can “stuff its gut”, literally, in one sitting;

Frozen crabapple — what could be better on a cold day?!

3) fruit passes through the gut rather quickly, compared to the protein and fat content of seeds or insect bodies, so the bird can go back and fill its gut again and again, until its fat stores are replenished;

4) plucking enough fruits to meet the daily energy quota is much less expensive than foraging for seeds or insects, and lastly

5) fruit-eaters that harvest dense patches of food (berry bushes or crabapple trees) have a lot of down-time, when they can economize on their daily expenditures by resting in sheltered areas, away from predators and bad weather.

So the next question might be:  is there enough fruit here to sustain Robins all winter?  What is their diet in the winter?

A high proportion of a Robin’s winter diet is buckthorn berries, along with fruits of the dogwood, honeysuckle, holly, Viriginia creeper, and waxy fruits of bayberry, juniper, red cedar, and poison ivy. 

The increasing infestation of northern forests by invasive Buckthorn seems ideal for overwintering Robins, who can feast on its fruits and return the favor by dispersing buckthorn seeds in their excreta.

As much as 85% of the buckthorn berry crop may fall directly beneath the shrub, so Robins, which like to forage at ground level anyway, have a high density food resource there as well.

So, why spend all the energy to migrate and have to compete with the locals and other migrants, when you can stay put with a nice dependable fruit crop at home and be first with the best nest site in the spring?  Winter Robins are so smart.

“I am so smart..S-M-R-T”. (Homer Simpson)

One man’s bane, another man’s blessing

False Wild Indigo (Baptisia australis) is a lush perennial in the pea family that puts out long spikes of large purple flowers in the early spring.  Even after flowering, it is an attractive plant in the garden because of its size and deep green leaves, — and the deer don’t eat it!

False Wild Indigo in the garden this June.

I happened to glance out the window in the direction of this plant this morning and was shocked to find that half of it has been reduced to gray, skeletonized, ashy leaves.  Had I completely forgotten to water it?

The same False Wild Indigo in August.

No, the poor thing has been attacked by a swarm of Genista broom moth caterpillars, who are slowly eating away almost all of the vegetation, and leaving webs of fine, silky threads everywhere.  The caterpillars are gregarious when small, but branch out when they get to be 1-inchers, leaving just webs and frass in their wake.  They do particularly well on legume (pea) species, and can reduce perennials and small trees to bare stems in a short time (the bane part).

There were at least 20 of these caterpillars, in assorted sizes from small to large, on just one branch of the plant.

The birds don’t seem to be interested in a juicy caterpillar meal. But then, perhaps the yellow and black aposematic (warning) coloration, and all those spiny projections sticking out from their bodies are sufficient warning to the birds.

What could possibly be a blessing about this insect? As it turns out, this species will develop quite nicely on a number of different species in the pea family, not just False Wild Indigo.  Several Genista Broom species are invasive, weedy plants introduced from Europe, North Africa, and Southeast Asia, and the Genista broom moth caterpillars love to eat them.  They are a built-in (native) biocontrol agent for invasive plants; and in California, where the various broom species have especially thrived, the broom moth can produce multiple generations per year — they are helping to check the broom invasion.

So while we here in the Midwest rail on about how they decimate our perennials, those out west may be grateful for their herbivory on all the Scotch Broom that covers the hillsides and displaces the native chaparral vegetation.

what is black and white and red..in places?

When we were traveling in Turkey, I got a few chances to photograph some of the wildlife, featured in a recent post, but largely unidentified.  Thanks to one of my savvy fellow travelers who found an image of one of the creatures on Flickr, I now have a name for the caterpillar I saw.  It turns out the species also occurs in the U.S., even in Minnesota, where it was introduced on purpose to control a noxious invasive called leafy spurge. (Below, leafy spurge was one of the earliest plants to emerge last spring near my backyard.)

This little beauty…is the caterpillar of the Spurge Hawk-moth (Hyles euphorbiae), seen in one of its native lands (asian part of Turkey) on one of its natural food sources, perhaps Euphorbia lambii, the Tree Euphorbia.  The plant is native to the Canary Islands, but has been introduced everywhere in the world as an ornamental.

In fact these spurge bushes were crawling with caterpillars, and they were doing a fine job of trimming back the green vegetation to bare sticks.  Black coloration with white spots and red trim makes the caterpillars really stands out.  When streched out, you can see green segments between the black and white.

Typically such eye-catching coloration is a warning to predators that the prey is inedible at the least, or poisonous at the worst.  Its host plants, the euphorb species, are toxic, especially the leaves.  However, sea gulls have been observed to pluck the caterpillars right off the euphorb bushes growing near the sea shore, so perhaps their toxicity is mild.

The adult moth is quite attractive with well-defined brown patches on the forewings and pink coloration on the hind wings.  They are day-flying moths (like other sphinx moths), and exhibit hummingbird-type flight when visiting flowers, hovering near the flower heads and dipping their long coiled proboscis systematically into each flower.

Photo from: http://ukmoths.org.uk/show.php?bf=1986

After mating, females lay clusters of up to 50 eggs on leafy spurge plants, adhering them to the stems with a sticky gum substance.  Easy to see why the plants we saw on our hike were covered with maturing caterpillars.

Photo from: http://en.wikipedia.org/wiki/Hyles_euphorbiae

Even if the caterpillars defoliate the spurge, the plants seem to recover quite nicely.  Unfortunately, the moth’s introduction has not provided the biological control for leafy spurge that was hoped for.

The corn farmer’s bane

We were out for a walk through the prairie a couple of weeks ago, and eldest grandson found a plant with soft, velvety leaves and asked me what it was.  I didn’t know, so he suggested we call it “velvetleaf”.  Well, what do you know, that is its name, because of its chief characteristic — the large, heart-shaped, velvet-textured leaves.

But it is distinctive for its unusual shaped seed pods as well.

Something this odd looking cannot be native, so I looked it up in the Invasive Plant species book, and sure enough, it is a terribly invasive weed, which explains why it was growing so well right at the edge of the prairie in the most disturbed ground.  It is also known as China Jute (for the strong fibers harvested from its woody stem) and Indian Mallow (pretty yellow flowers in the hibiscus family which apparently smell fruity).

(Photo from Wikipedia)

Each seed capsule is multi-compartmented, and each compartment contains 2 or 3 seeds, so each plant can produce a large number of seeds.

And that’s where the bane of the farmer comes into this story.  Velvetleaf is an aggressive invasive in croplands, especially cornfields, and can decrease corn yield more than 30% if left untreated.  Here in the midwest we see lots of TV ads in the summer for various herbicides, and now that I think about it, they all promise to “eradicate velvetleaf”.

But on the prairie, velvetleaf has to compete with native grasses and forbs that cover the ground in a dense mat of vegetation, so it seems relegated to the edge of the fields.

Mating balls

They are back, and I’m not happy about it.  Last year, I first noticed a few Japanese Beetles on the raspberries on July 14.  This year they showed up last week, about three weeks early.

Japanese Beetles have been moving westward in the U.S. since the early 1900s, but have really taken off in Minnesota (at least in the Twin Cities area) in the last two years. And they can do some serious damage while foraging on their favorite foods, leaving skeletonized leaves behind.

The really destructive potential of these insects is their propensity to aggregate in huge numbers together in large mating balls.  The female pheromone attracts both males and females who not only share a few gametes but keep right on eating while mating.  Here, they have devoured a white rose.

This year I unknowingly added to their favorite food sources by planting apple trees in my front yard.  Now they have a gourmet platter of raspberries, roses, and apple trees to choose from.  So, how can I control the damage?

The USDA website provides a handy publication on management of japanese beetles including a list of the susceptible and non-susceptible plants (click here). For beetle control, this publication recommends only a variety of toxic chemicals, introduction of other pests, or fungal/bacterial agents sprayed on your lawn to control the beetle.  In addition, the major flaw of this type of management is the fact that you can kill all the beetles one day or suppress their development in your lawn, and more will simply disperse to your yard to replace them.  Chemical sprays are a poor solution because they are not selective and kill many types of beneficial insects as well.

This is my solution to the problem, at least for now until I find something better.  Using what I now know about their daily movements (between plants),  I go out several times a day and walk around the plants carefully flicking all the beetles I find into a cup of soapy water.  Mating balls tend to form on the apple trees about mid-day during the peak of their daily dispersal, and I can collect huge numbers of them before they do significant damage.  By late afternoon there are far fewer beetles on the plants (perhaps only the ones I missed earlier), and after collecting those, I haven’t found any more beetles on the plants until they start dispersing the next day.