The Goats That Ate The World

Invasive plants and animals are part of the curse of modern forms of transport and trade .....

Nothing Can Eat The Poisonous Cane Toad And Live .....

.... and the cane toad in Australia is perhaps the poster boy of introductions that have gone spectacularly wrong.

Boomerang Effect

I have not followed the Cane Toads in Australia story for quite a while .... last time I looked, they were still expanding their range, but it was hoped that natural obstacles such as deserts, and mountains, would mean that even if man couldn't halt them, natural geography would.

No, Not This Common Toad .....

 

This would mean that the south and western parts of the continent would (barring accidental introductions via cars, trucks, trains, or crate packages), remain free of the pest.

 

Of Women and Toads

John Steinbeck made an animal connection for mens behaviours in 'Of Mice and Men', so the question is 'What do the Cane toads of Australia and the women pioneer settlers of the old Canadian and American frontiers have in common?'

I'll bet you haven't guessed, so I'll tell you its the fertility (or fecundity) of each wave of settlers ... yes apparently scientists and researchers have managed to link these two apparently disparate topics, with some detailed analysis of the well kept marriage and birth records of the French settlers of Canada (which go back to the 17th century), to show that women who were first to settle in a new land had more children and grandchildren than those who followed later.


French Candian Settlers with high birth rates

Now why this is a surprise to anyone beats me, anyone in Europe watching immigrants arrive in the last 35 yrs will have noted that they have larger families than the natives, and similarly in the US, the Latino immigrants into the USA have larger families than the natives, but in most cases their children have smaller families as each generation reproduces until they reach the norm for that area.

The main difference between this casual observation, and the research findings, is that they managed to show that woman who arrived as part of the first wave of immigration into an area had 15% more children than those who arrived a generation later ..... apparently pioneering woman married younger and benefited from scooping up the best local resources, and their daughters inherited their mother's higher rate of fertility. They then showed that women who came with the later immigration wave that arrived 30 years afterwards, did not exhibit the same fertility rates as the first wave and their offspring.

The Hatfields were a fertile pioneer settler clan in the Tug valley.
Who famously clashed with the similar McCoy clan.

So how have they managed to link this analysis, with the menace of the outback (I have posted on these creatures on more than one occasion), the cane toad, and thus allowed me to also link this post with them?

Well apparently, scientists have observed that the cane toads at the edge of their range have bigger front legs and stronger back legs; making it easier for them to invade new areas. Then when these pioneer cane toads at the frontiers breed, their offspring also inherit these bigger and stronger limbs. However, other cane toads who migrate into these areas after the first wave, don't exhibit these physical attributes.


Fertile Cane Toads - doing what they do best

Apparently this effect was not unexpected, but no one until now had been able to show this phenomenon operating in human populations .... the point of all this research (if there is one) is that families at the front of the wave of migration contributed more to the contemporary gene pool, than those that were slower to arrive and this explains why pockets of certain rare genetic diseases carried by the first settlers still exhibit in some areas to this day (so now you know!). 

Cane Toads Australian Invasions Halted?

A while back I blogged on the rise and conquest of the Cane Toad in Australia.

At the time it looked as though nothing could stop them, and I even entered into correspondence with scientists in Australia who were trying to control them .... I was interested in the story and their plans.

Anyway, this week came some good news, some parts of Australia maybe 'too cold' or 'too dry' for the Cane Toads to advance into these areas. This story on the BBC, offers hope that some areas may survive the Cane Toad invasion and allow scientists a chance to develop control methods.

However a note of warning, the toads have proved very adaptable so far, and may yet find away around difficulties e.g. accidental introductions bypassing natural barriers or even local wet periods, or warm spells temporarily removing the obstacles.

The danger still remains that they will get into the major river systems in the south of the continent, or the permanent water sources like those in the West MacDonnell Ranges and the Pilbara in the interior and adapt to local colder water conditions (after all, turtles manage to do this in the UK and are now thriving).

But its still some good news for the local wildlife and may yet prove to be a temporary answer for some areas, but somehow I suspect this adaptable invader may yet find a way past this obstacle.

The Irresistible Cane Toads (Conquerers of the Outback).

The Problem: The Cane Toad (Bufo Marinus) is Australia’s greatest ever threat to native fauna since man arrived.

The History: Introduced as a pest control in the sugar cane fields in the 1930’s it spread quickly and finding no predators, has now reached approx 200 million spread over Northern Australia, and because the are

• Very poisonous (they have a toxic skin), and kill predators that eat or bite them, and
• Voracious predators and will eat anything that they can get their mouths round e.g. Small mammals, insects, fish, Chihuahuas etc etc.
• The breed like hell, and with no predators the young survive in massive numbers.

 

They are a very real threat to native species diversity. They have few predators in their native Hawaii and are controlled by illness, rather than Hawaiians species. Introducing new bacteria’s would be risky and in any case their range is too great now.