|
|
Post by papilio28570 on Mar 14, 2013 19:07:45 GMT -8
|
|
|
|
|
|
Post by nomad on Mar 19, 2013 10:52:45 GMT -8
Truly alarming indeed.
|
|
|
|
Post by boogtwo on Mar 19, 2013 12:04:03 GMT -8
The largest single year drop of the main North American continent population, but they have been in a steep decline for about a decade. It is estimated that from 1997's estimated population, it is now down over 93%. As always, habitat loss, herbacides and pesticides, possibly weakened before wintering by them and OE parasites. Could/would be a lot worse if some organised efforts to save them had not been in place. But it was not enough with three nations all having to be on the same page doing so working together. They probably never will be either in time to save them. I don't have the exact numbers on the western race, but they too have been in decline since at least the late 60's/early 70's that I have personal field experience with. Groves that I studied along the CA coast myself continued to spiral down, some I visited are no longer used at all.
|
|
|
|
Post by Adam Cotton on Mar 19, 2013 13:09:49 GMT -8
There is NO western race of the Monarch, recent DNA analysis (Lyons, Pierce, Barribeau, Sternberg, Mongue & de Roode (2012) Molecular Ecology cited at www.monarchlab.org/mn2012/Admin/upload/22.pdf - sorry I don't have the page numbers) has shown that they are genetically identical and there is gene flow between east and west, it's a total human construct, the idea of an eastern and western race of plexippus. Yes the monarch numbers are in decline, but that is really due to the same problems as all (or most) other butterflies - pesticide use, destruction of habitat, BT spraying etc etc. However, try going to www.monarchnet.org/ , click on Data and generate a graph for Cape May, New Jersey. The graph shows no decline in the abundance of fall migrants passing through Cape May since the annual census began in 1992. This actually suggests that at least in certain places numbers are stable. (This information comes from Paul Cherubini.) I would suggest that news articles such as the one in the 1st post of this thread (and many others) are often misrepresentations of the truth (often deliberate and for specific reasons) - 'scaremongering for a purpose' - sometimes purely as a tool to obtain funding (although I am not specifically saying that it is the case in this article or similar stories). I think you will find that the monarch will find a way to adapt and survive ad infinitum, maybe in larger or smaller numbers, then when humanity has finally gone they will still be here and their numbers will balance with the environment again. Adam. |
|
|
|
Post by wollastoni on Mar 19, 2013 13:28:38 GMT -8
Adam, I am afraid you are too optimistic.
When humanity will be gone, there won't be a single flower or butterfly still alive...
|
|
|
|
Post by froggy on Mar 19, 2013 13:56:44 GMT -8
Adam,
Thanks for the monarch link. Very interesting to see the normalized population histories. Looks like widely fluctuating populations from year to year.
I think 2012 must have been a fairly good year for the eastern US monarchs: Around southern Maine and the Boston area, we saw many more individuals flying south this past September than in several previous years. A few years back, we had the pleasure to have a gorgeous Monarch Pupae in our backyard (we have a few wild milkweeds plants). Unfortunately I missed this butterfly's departure as I was away from home for a few days...
Thierry
|
|
|
|
|
|
Post by boogtwo on Mar 19, 2013 17:25:20 GMT -8
Adam,
I think most understood I meant the western population, but thank you for correcting my mistype.
|
|
|
|
Post by Adam Cotton on Mar 20, 2013 0:45:22 GMT -8
boogtwo,
No problem, but there has been a long-term misunderstanding that the western and eastern monarch populations are totally separate without genetic interchange. This has now been shown to be untrue, along with recent observations of the numbers of butterflies crossing from east to west (or the opposite direction) during the summers.
It is also interesting to note that when the monarch was introduced to Australia and New Zealand it instinctively set up migration routes and roosting sites in those countries too.
Adam.
PS. Olivier, sadly you may be right.
|
|
|
|
Post by admin on Mar 21, 2013 8:50:17 GMT -8
boogtwo, It is also interesting to note that when the monarch was introduced to Australia and New Zealand it instinctively set up migration routes and roosting sites in those countries too. Adam. Really? Tell us more. |
|
|
|
Post by wollastoni on Mar 21, 2013 9:53:15 GMT -8
In 2009 in the Baliem Valley, West Papua, we met a small colony of Danaus plexippus in the remote Dani tribe's village called "Wamerek" at about 1600m altitude. There were plenty of them flying in Dani's plantations.
I am not a specialist of this species, but they seemed to use an hostplant cultivated by the natives for food.
|
|
|
|
Post by Adam Cotton on Mar 21, 2013 11:57:38 GMT -8
Clark, I found this online : www.sciencelearn.org.nz/Science-Stories/Butterflies/Monarch-butterflieswhich includes "Adaptations to life in New Zealand Monarchs in New Zealand do not follow the same migration pattern as their northern relatives. They have adapted their migration behaviour to suit local conditions. When the air temperature drops to 12.8°C, monarchs flock together in overwintering sites. These sites tend to be in milder coastal locations where the temperature remains at least 10°C. Overwintering monarchs prefer sites that are sheltered from the wind, have trees with a rough bark surface on which to cling and have a nearby source of nectar. The butterflies are mostly inactive, but on warm days, they fly, bask in the sunlight and feed. When the temperatures warm up, butterflies move inland to reproduce. Swarms form regularly to overwinter at places such as Tauranga Bay in Northland. The Monarch Butterfly New Zealand Trust (MBNZT) was initially formed to protect this site. Other overwintering sites include areas of Hawke’s Bay, Nelson and Christchurch. The MBNZT encourages citizen scientists to tag butterflies so we can learn more about the migration and overwintering habits of monarchs." The following webpage: australianmuseum.net.au/Wanderer-Butterflyhas this information on monarch migration in Australia "Seasonality In summer, Wanderers are found throughout their range along the east coast of Australia from Queensland to South Australia, and in south-west Western Australia. They have also been found in isolated parts of the Northern Territory. They are strong fliers and can cover long distances during their adult life, which is about a month to six weeks in summer. During this time they can move to unoccupied areas to find new plants on which to lay eggs. They take nectar from flowers to maintain their energy levels as they go. As winter approaches, the butterflies leave the inland areas as temperatures drop and migrate towards the coast. For Wanderers near the coast north of the Richmond River in New South Wales, breeding can continue for most of the year with one generation following another. Further south, adults that develop in autumn do not breed immediately. They remain in a non-breeding state throughout winter, some of them staying in the same district for several months. In cooler areas, these non-breeding adults may gather together and hang from the branches of trees in large clusters of thousands of butterflies. This is known as over-wintering. The same trees are used for this year after year. The clusters are at first made up mainly of males. The females arrive a week or so later. During the warmth of the day the butterflies fly around the trees, but with the afternoon drop in temperature they settle to reform clusters. Cluster sites are known in the Sydney Basin and Hunter Valley, as well in the Mt Lofty Ranges, near Adelaide. The clusters appear in about April and remain until about August or September, when the butterflies disperse after mating. The females are the first to leave, moving off to lay the first eggs of the new season on fresh spring growth. Succeeding generations extend the range across the country until the full summer range of the species is again occupied." Adam. |
|
|
|
Post by wingedwishes on Mar 21, 2013 13:51:13 GMT -8
I think the genetic modification of grain may play a role as well. I thought the University of Kansas developed herbicide resistant corn or wheat. When planted in huge tracts, herbicide is able to be sprayed in the fields to kill weeds (milkweed) in the growing area. With much reduced food sources, the migrant leps had no place to lay eggs.
In my region of Florida, they are doing very well. I think they have also been introduced into areas such as the Bahamas.
|
|
|
|
Post by wollastoni on Mar 22, 2013 3:31:22 GMT -8
Yes herbicid resistant GMO are a big theat for monarchs (and millions of other insects...)
|
|
