Wildlife Photographer of the Year: monarchs at sunset
The light was fading fast at the El Rosario Biosphere Reserve in Mexico, as photographer Jaime Rojo grabbed his camera and ran up the slope past trees trembling with hundreds of thousands of butterflies.
The result was his remarkable image, Magnificence of monarchs, which earned him a finalist position in the Animals in their Environment category of Wildlife Photographer of the Year.
A North American icon
Eastern monarch butterflies are a large population of the species Danaus plexippus, which journey from their breeding grounds in the northern United States and southern Canada to overwintering sites in northern Mexico. Their migration is one of the most extraordinary stories in nature.
'Going to see the monarchs was the first thing I did when I moved to Mexico. For me it was one of those must-see wildlife spectacles,' says Jaime, who was born and raised in Spain.
'Colonies can be incredibly chaotic and it can be difficult to isolate a good photograph, but during this trip in March 2013 I was able to capture a really special image.'
Jaime says, 'I had visited the monarchs many times before, but this time I was working with a film crew for a documentary, and we had a permit to stay at the colony beyond the usual strict cut-off time of 16.00.
'It was getting quite late and I saw the potential of the light, so I grabbed my tripod and ran up the hill to get a few shots of the colony.
'It was very dark, but I managed to capture this unique shot with the colony backlit by the setting Sun. I had never seen something like this in all my years visiting the monarchs.
The special moment came as one butterfly spread its orange wings and the rest of the colony filled the frame.
March of the monarchs
Monarchs are perhaps best known for their epic migration undertaken by millions of individuals. A full cycle can span at least four generations.
After spending the winter months in Mexico, successive generations of monarchs migrate northward, breeding and replacing their population as they advance.
When the third or fourth generation finally reaches the most northerly part of the monarchs' range, exposure to falling autumn temperatures causes a special generation of monarchs to undergo a physiological change known as reproductive diapause.
These butterflies live four or five times longer than the northward-migrating predecessors, allowing them to make the almost 3000-mile journey south to Mexico to pass the winter, before starting the cycle again.
Some monarchs instead travel south-east toward Cuba or south-west toward California, but the Mexican migrants are really special for the sheer sizes of their roosts.
Protecting the monarch
The migratory monarch population has suffered a significant loss in numbers in the last 20 years, with an 84% decline recorded in the average number of monarchs per overwintering site in Mexico recorded between 1997 and 2011.
Illegal logging of the monarchs' preferred habitat, the Mexican oyamel fir tree, was once the greatest threat the migratory population faced. But even when logging activity was significantly reduced, the decline continued.
It is now understood that changes to forest microclimates in Mexico, the loss of milkweed habitat in the United States through the use of agricultural herbicides such as glyphosates, extreme weather events, climate change and overexploitation of water resources near the roosting sites are all contributing to the sharp reduction in monarch numbers.
Several citizen science and conservation projects are underway to stimulate recovery. These include the construction of milkweed waystations along the migration routes - a plant which is vital to the butterflies' reproductive cycle.
David Lees, butterfly curator at the Museum, says, 'The monarch is remarkable in that the caterpillars eat the leaves of the milkweed and the plants still favour the butterfly as its most important pollinator, which is powerful enough not to get its legs trapped in its flowers.'
A butterfly effect
Not only does Wildlife Photographer of the Year showcase the most beautiful phenomena in nature, it is a powerful tool for communicating important messages about the natural world.
Jaime says, 'Despite the abundance of butterflies in the frame of the photograph, 2013 represented a particularly low year for monarch numbers in overwintering sites.
'I hope my image and the story of the monarchs reminds people that the small things matter. Very few people are aware of the massive decline of insects worldwide, something that could have catastrophic consequences.
'It's a butterfly effect. Small changes can end up having a big impact on a species.
'I think Wildlife Photographer of the Year has a critical role to play in highlighting the many challenges facing the natural world, and not just to portray the beauty of our nature.'
Visit the exhibition
The fifty-third Wildlife Photographer of the Year exhibition, showcasing the world's best nature photography, is open until 1 July 2018.