Mexico – The Butterfly Effect

We have just returned from an amazing trip to Mexico, a holiday arranged with Naturetrek ostensibly to experience the wonders of the monarch butterflies overwintering in the oyamel pine clad mountains to the southwest of Mexico city, but there were many other delights to savour which I will write about soon. For the present, I bid you welcome to the first of my blogs from Mexico – The Butterfly Effect.

The horse took one look at who it had to carry up the hill, snorted in derision, weighed up its chances of bolting but eventually accepted its fate. The overweight Brit clumsily clambered aboard and off we trudged, the horse grumbling under its breath at the unfairness of life; its rider trying to act as though he knew what he was doing while having not a clue. A Surefooted beast it turned out to be that, together with a herd of its brethren, unerringly transported me and the rest of our group to the staging post at an elevation of 3200 metres at the Piedra Herrada Monarch Reserve,  beyond which the gradient became too steep and fractured for our equine pals. We braced ourselves for the hard work. Each Furnished with a stout wooden pole we began the slow trudge towards the mountain peak, avoiding tree roots and loose rocks, stopping every few minutes to catch our breath and allow our wildly beating hearts to settle. It was exhausting labour, but then a flutter amongst the dense foliage, and another, and yet a few more showed we were nearing our prize. And all of a sudden there they were, monarch butterflies, thousands of them dancing through the glade, smothering the nectar bearing flowers of shrubs and plants, jostling for prime position to sample the life sustaining liquid. What a sight!

The monarchs undertake a momentous 3000 mile migration every autumn, funnelling southwards from Canada and the USA into the cool mountainous regions of central Mexico. The butterflies arrive in late October just before the legendary El Dia de los Muertos – Day of the Dead – celebrations which are held annually on 2nd November. Their timely appearance fosters the belief that they enshrine the souls of ancestors, thus endearing the monarchs to local peoples. This migrating super generation does not fully mature but spend the winter huddled together on the trunks of trees, or forming clusters on the extremities of hanging branches. When the sun shines they venture forth to find nectar or water, decorating the skies in their fluttering millions. On this, our first day in the forest, our arrival coincided with a spell of sunshine encouraging the insects to float through the forest like so many autumn leaves. But their safe tenure here in the mountaintops is sandwiched between potential climatic threats. If it gets too warm too frequently the butterflies can reach sexual maturity too soon resulting in a disrupted northwards migration and breeding season. If the climate becomes too wet and cold, these bright orange Lepidoptera can literally freeze to death in their thousands. Both scenarios represent real and present danger. Illegal logging can also result in either total destruction of the wintering grounds or a subtle disruption in the micro climate the monarchs need to successfully survive the winter.

When spring beckons the monarchs fly northwards, moving into Texas where the first of 3 or 4 generations will be bred. The overwintering insects will die soon thereafter, their role in life complete, leaving their offspring to leap frog their way across the continent of North America to grace milkweed plants for another year. Here, another threat awaits them in the form of such things as intensive agriculture and increasing urbanisation, both resulting in reduced feeding and breeding opportunities. It’s the same old picture that afflicts wildlife the world over; man’s stupidity and greed impacting nature to a sometimes irreversible degree.

Come autumn this amazing cycle recommences, providing the magical spectacle we were lucky enough to witness on this day in the deep pine forest where the air is thin and my horse wished I was. How the migrating generation knows when and where to migrate is a mystery that still baffles science. After all, this collection of insects is separated by 4-5 generations from those that made the journey the previous year, yet still find their way unerringly to those pine forests in Mexico. It’s akin to a human child knowing the way to its ancestral home occupied by its great, great, great grandparents without ever being told in any form understandable by us. A truly awesome feat – and I never use that adjective that is nowadays so often misused.

Despite the many challenges confronting the monarchs, it seems we are at last entering more enlightened times. Eco tourism is the stimulus for this change. Local communities are proud of their position of custodians of one of the worlds great natural spectacles and now take a keen interest in sustainable living. Income is derived from assisting tourists with the ascent, providing food and drink facilities, souvenir shops and so on. Local people act as guides and a form of cooperative agriculture ensures relative prosperity. Local law enforcement has been stepped up as well, resulting in an almost total eradication of illegal logging – a major step forward.

The fate of these spectacular creatures is, for the present time, stable. At least as far as direct human interference is concerned. Whether ongoing climate changes result in longer term damage remains to be seen. I have a feeling nature will find a way as long as the butterflies are left to sort it out for themselves.

Certainly on this warming day they provided thrills and pleasure to all who were able to make the steep climb. Even our outward BA aircrew with a couple of days on their hands before the return flight to London had made the journey. They, like all of our party left each with a smiling face and happy memories to take back done the mountain, leaving the butterflies to bedeck the flowers and feed while they could, because the warmth of the day would slowly ebb away to leave them huddled together to collectively survive another night amidst the chill of the mountain.

The relatively gentle stroll back down the mountain was enlivened by being able to occasionally latch onto various small warblers, both resident and migratory, that choose to spend the winter at these high altitudes. It’s always difficult to get a good look at small birds tazzing around in dense foliage, but with patience we were rewarded with some colourful gems.

Our second monarch spectacular took place some miles to the south, and provided a complete contrast to the first. This day was cool and largely overcast, resulting in the insects remaining in their clusters awaiting a burst of welcome sunshine that didn’t arrive. The horse ride to the overwintering site was much easier (for the horses) leading across largely flat alpine pasture before plunging into and under the pines. The drop off point was also much closer, which at an altitude of 3,400 metres was a blessing. No mass of flying insects today, instead we were treated to the mind numbing sight of countless thousands of butterflies packed closely together on tree trunks and clustered along boughs and amongst shrubs. The sheer numbers involved was hard to comprehend, although it appears the overall population is significantly reduced from recent years. This may simply be a cyclical fluctuation. Imagine though, if you will, looking at the trunk of a large tree that appears gnarled and knotted as befits its age and stature only to realise that what you took to be bark is in fact butterflies, stock still, torpid and on the edge of existence. Through binoculars the bold black network of veins on the underside of ranks of silvered wings makes your jaw drop. Nothing of the tree itself can be seen, every inch is covered. On occasion a stray insect will try to muscle into the cluster, forcing its way between the already tightly packed bodies to become just one atom of the collective.

On the fringes of the massed hordes, satellite groups adorned low growing shrubs and grasses. Below them, sadly, the bodies of less fortunate tribe members lie still. Even in good conditions mortality runs high, but the strategy of massed overwintering has worked for the species for millennia. Let us all hope it remains a valid and profitable option for these glorious insects for millennia to come.

For more blogs concerning butterflies, including identification guides click here.