Re-establishing the natural balance - Americas and Exotics

[Toddy]

This thread has been separated from the original. The original thread started in Flora and Fauna with this post about red squirrels in the UK. It rapidly evolved, or devolved, into a predominantly three way conversation that focused on North American fauna with the occasional mention of exotics and UK species, but all through a non UK lens.

This thread has been created to allow that conversation to continue. The original thread remains for anyone who wishes to talk about the UK conditions and situations. CC




From the BBC Scotland website.
http://www.bbc.co.uk/news/science-environment-43308588

The growing numbers of pine martens have actually helped the red squirrel population because the martens seem to take out more of the grey squirrels, which did not evolve alongside cat sized, tree climbing predators.
The Reds did, and seem to manage despite the pine martens, while the greys, which are much more likely to ground forage too, are predated upon and their numbers are reduced where the martens are thriving.

Interesting, and unexpected results

M

 

[Robson Valley]

It's an Arms Race = Predator and Prey. I don't think you would be at all surprised to see just how similar their skeletons are.
Prey are not extinct. Predators cannot kill them all. In fact, ecosystem studies commonly show that the predators get about 10% of the prey.
Yes there are a few aquatic exceptions of far greater efficiencies which can be ignored in terrestrial circumstances.

 

[santaman2000]

It's an Arms Race = Predator and Prey. I don't think you would be at all surprised to see just how similar their skeletons are.
Prey are not extinct. Predators cannot kill them all. In fact, ecosystem studies commonly show that the predators get about 10% of the prey.
Yes there are a few aquatic exceptions of far greater efficiencies which can be ignored in terrestrial circumstances.

That's true of naturally evolved prey/predator relationships. However it flies out the window when an introduced predator gets to prey species with no evolved defenses.



Brown Tree Snake

Brown tree snake (Boiga irregularis)
Regulatory Status: Hawaii Injurious Wildlife. Federal Injurious Wildlife

Not known to be established in Hawai’i, Call 911 immediately to report any snake sighting

Description

• Snake with yellowish to dark brown back, sometimes with mottled bands. Underside is cream to yellow colored.
  
  
• Head wider than body, with eyes that are cat-like (the pupils are vertical)
  
  
• Night-active, lives mostly in trees, although frequently seen on the ground.
  
  
• Length is 45 cm (18 inches) when first hatches from egg, may grow to 3 m (9 feet) in length, although most frequently 1-2 m (3-6 feet)
  
  
• Able to reproduce at three years age, BTS lay
  
  
• Native to the South Pacific including the Solomon Islands, New Guinea, and Northern Australia. Believed to have been accidentally introduced to Guam in the 1940s hidden in cargo.

Impacts

• On Guam the population of brown treesnakes is not controlled by predators, diseases or competitors as it is in the snake’s native range. The current population estimate is about 50 BTS per hectare.
  
  
• BTS eat birds, bird and reptile eggs, lizards, small mammals such as rats and mice, and even small household pets. They are responsible for the extinction of 9 of 13 forest bird species and three species of lizard. Other species of birds have been reduced to very low numbers and seabirds such as terns, noddys and shearwaters no longer nest on the island.
  
  
• In the absence of preferred prey (birds, small mammals), BTS have switched to feed on lizards and skinks, which reproduce faster and are able to sustain the snake population at abnormally high levels.
  
  
• Ecological impacts of the absence of birds and lizards (largely insect-eating species) include a rise in the abundance of insects, which may affect crop production.
  
  
• The brown tree snake causes frequent electrical power outages by climbing power lines and getting into transformers and electrical boxes. Snakes have caused more than 1600 power outages in the 20-yr period of 1978-1997 and most recently nearly 200 outages per year. Costs to the island’s economy have exceeded $4.5 M per year over a 7-year period without considering transformers, and damages inside electrical substations.

Distribution:

• Not known to be present in Hawaii at this time, although a total of eight brown treesnakes have been found live or dead in Hawaii between 1981 and 1998. All snakes were associated with the movement of civilian and military vehicles or cargo from Guam. No special searches were conducted for cargo or crafts as they were leaving Guam or arriving from Guam in Hawaii prior to the 1980s, as the problem on Guam was still coming to light.
• An economic study by the University of Hawaii estimated that the introduction of the brown treesnake to Hawaii could cause between $28,500,000 and $405,000,000 annually. A new assessment by the USDA National Wildlife Research Center puts the actual cost of BTS at $1.7 billion per year if introduced to Hawaii.

What you can do
If you see a snake, call 911 or 643-pest immediately!

For more information, see:

• Boiga irregularis Datasheet from CABI
• Boiga irregularis information from HEAR
  
  
• Boiga irregularis information from ISSG
  
  
• Boiga irregularis information from USGS Fort Collins Science Center
  
  
• Boiga irregularis information from National Invasive Species Information Center

 

[Robson Valley]

Of course 100% of the prey eventually die. So does 100% of the predators. What does their survivorship curve look like?
That's independent of any particular cause such as predation, disease or misadventure.
Fish, Robins and Humans do not share a survivorship curve by a long shot. Three classic structures.

You cannot point out the mis-managed introduction of prey species or predators as examples of what's normal.
You really need to see what foxes and pigs and rabbits and cane toads have done to the Australian outback.
I looked at it all for 4 years. I don't welcome introduced or feral species.

Both prey and predators have reproductive strategies which sustain their populations at what is called 'n' ,
a size less than 'K' which is the absolute maximum carrying capacity of the environment.
Without serious numbers from mark/recapture population studies, the interactions are best shown
with a deck of playing cards on a bar table.

As innocuous as it may appear, we have a large summer population of a 2-spot Lady bird beetle species.
They were brought over from Asia for aphid control in vegetable crops as they are rapacious feeders and breeders.
Since then, it appears that they have been able to out compete native species. What shall we do? Embrace extinction?

 

[santaman2000]

.....You cannot point out the mis-managed introduction of prey species or predators as examples of what's normal.....

Introduced species are the sole point of this thread.

 

[Robson Valley]

The local deer stand on my doorstep. I see their footprints in the winter snow.

a) I use an emulsion spray called Plantskydd for my grape vines. Once dried, it seems to stick to the leaves for a couple of months.

b) The forestry/lumber/logging giant Weyerhauser bank rolled a couple of university graduate students to do the research work to find an economical
deer repellent that would protect the conifer seedlings after planting out. All they will say is that powdered egg is one ingredient. Maybe they sell it.

c) The apple trees are behind a 6' fence. There's a slack tape across the top that flutters in the wind.
The deer won't jump the fence because they can't decide where the top edge is.

 

[Janne]

Plantskydd. Translated from Swedish: Plant protection.

 

[santaman2000]

Well. You're hooped. Big or little, the gaffes abound.
Pass the Boas, Santaman. How's that going?

Another principle in population ecology is that, in competition,
the winners overwhelmed their competitors by sheer numbers.
I'm discouraged to watch feral species success.

Me too. The Burmese pythons are just one of a long list we have to contend with: Lionfish, feral hogs, coyotes, Fire Ants, and even a Cuban lizard. Then there's a bucket full of plant species.

I can always tell when the hawk is about. The wee birds go absolutely silent, and they coorie down on the ground, huddled tight to the grass....

You should see the cat freeze when he sees a hawks shadow go by. Small dogs get taken every now and then.

 

[Robson Valley]

I have family in Grand Bahama. Divers.
They kill and eat all the Lionfish that they can spear.
Taste good and never any bag limits.

Is it not just a Hell of a thing to have to put up with these critters?
Thing is, you can' kill enough of them by any means to make a difference.
Blast away, kids. Might as well eat a few.

 

[Janne]

They are here too. Very tasty! Good in a Fish Curry. Or pan fried on a sandwich.
They are trying to teach the sharks to eat them, with some success.

 

[santaman2000]

Same here: no bag limits, no size limits, no closed season, etc. Still can't really make a dent in the population though.

 

[Janne]

Hell no.
They discovered here last year that they live really deep on The Wall, and migrate up. Deeper than any human can go.

The Grey Squirrel is nothing compared to the Lion Fish. They eat all the other reef fish to extinction.

 

[Janne]

Yes. I believe too that the eco system has changed to accommodate the greys.
if they should be completely removed, the ecosystem will change again. Then the Reds will spread - ecosystem will change again!

Nature is hugely adaptable and will find a way. It has done since the formation of the first living cell.

 

[daveO]

Florida sounds like a free-range pet shop. When I was a kid I begged my mum to let me have an iguana but they were too expensive. In Florida now they're falling out of the trees.

 

[Robson Valley]

You couldn't do it if you tried.
I see that most everything in the UK is owned by somebody that you can name.
Trespass would choke off any sustained efforts.

I'd like to watch anyone with 1 or more air rifles( in locked cases) try to sneak out of London on a train.
Coming back with a sack of dead squirrels would be just as funny.

Here, there are huge tracts of landscape with no people and no roads.
A proper fishing and/or hunting licence for the correct season and away you go!
Drive up some all-weather logging road for 20km. Stop, Park, Go for a walk. Shoot some grouse.
Catch a couple of trout. Go home and make supper. Fish and fowl.

Use Google Earth to fly around my place.
Sure, the flat land in the valley bottom is mostly cleared for some sort of agriculture.
If you want, I can give you adequate flying instructions to follow me 40km into the Holmes River valley.
You will not want to leave any time soon.

 

[Robson Valley]

There's very clear fossil evidence of a great diversity of mega fauna ( mammoths, etc) all across North America.
Many thought to be extant less than 10,000 years ago. Did Paleo Man drive their extinction or not?
Paleo Man was certainly very well established by 14,000 BCE. Then what?
Bison narrowly missed the cut and have thrived.

There's really 2 levels of extinction with respect to population size.
1. The first one is genetic, it has to do with the fitness of the remaining breeding population.
Some claim that n = 300 for humans. Pestilence and/or starvation are the usual drivers.

2. Below some number, 'n' there are not enough of them left to even find each other for breeding purposes.
Now, it's just a matter of time to watch their survivorship curve play out.
As the last ones age out of the reproductive age class, they are done.
This is one of the supreme tests of any captive breeding programs and I applaud every attempt.

 

[Janne]

One of the islands of Cayman Islands, called Little Cayman, population about 180.

If you are a Little Caymanian, you are lucky to be born with approx 5 fingers on each hand, never mind if they are fused....

 

[Janne]

Our Blue Iguana project has secured the future of retarded Blue Iguanas.
True, but you will not read about that!
Inside info.

 

[Janne]

Before humankind, Britain was part of the European landmass, not an island, mainly ice covered, so all the big (and small) tundra animals were there.
Must have been a beautiful sight!

Check out what grows on the tundra. Think Northernmost Scandinavia/ Greenland. So no forests of high trees. Shrubs. Maybe the Arctic form of Birch.

 

[Broch]

Before humankind, Britain was part of the European landmass, not an island, mainly ice covered, so all the big (and small) tundra animals were there.
Must have been a beautiful sight!

It's still a beautiful sight in many places