This article is available on a CC-BY license via Zenodo.
Cite as: Khrouf, H., Hogenhout, S., & Kamoun, S. (2025). Eight things we learned in Costa Rica. Zenodo. https://doi.org/10.5281/zenodo.14609309
We spent this year’s holiday season in Costa Rica, marking our first visit to Central America — a region renowned for its incredibly rich biodiversity, with about 5% of the world’s species said to be found here.
The trip exceeded all expectations. We were guided by exceptional local experts and saw new species every single day. We observed an astonishing variety of mammals, birds and reptiles. Even the insects and other invertebrates impressed, with beetles — naturally — capturing most attention. And the plants? Well, we’re not ones to suffer from plant blindness, and they certainly didn’t disappoint either.
Here are eight fascinating natural history vignettes that inspired us.
2025: the year of the snake
While in Costa Rica, we welcomed the new year surrounded by lush tropical scenery. On January 29, the Lunar New Year will officially mark the start of the Year of the Snake — a special year for one of us, born in 1965. In Chinese horoscopes, snakes are celebrated for their ability to shed their skin and renew themselves, symbolizing transformation and rebirth.
We can’t say just yet that our trip inspired us to shed our old skin, but it certainly kept us alert to the presence of snakes. Hotel management heightened the intrigue by showing us a photo of a boa constrictor that had dramatically fallen from the roof onto the restaurant floor, adding a touch of excitement to the dining experience. One of the restaurant staff, Hector, collected photos of snakes on his phone and had many anecdotes to tell. With stories like that, keeping an eye out for these mesmerizing creatures became part of the adventure!
As a natural bridge between North and South America, Costa Rica’s fauna and flora draw from both subcontinents. With about 140 species, snake diversity reflects this unique biogeography. Here, you can find the North American rattlesnake alongside the South American bushmaster. While we didn’t encounter either of these, we did spot the slender and graceful Brown or Mexican Vine Snake Oxybelis aeneus making its way through the Dry Forest of the Área de Conservación Guanacaste (ACG) along the Pacific Coast. Near Upala, located in the Alajuela province between the Miravalles and Tenorio volcanoes, our guide Stefani — a snake lover herself — spotted an Eyelash Pitviper Bothriechis schlegelii resting among the vegetation and conveniently willing to be photographed (see below).
Parakeets: make sure to eat your termites
We all know how important protein is in our diets. High-protein diets like Atkins and Paleo have been popular for years, touted for their benefits in building muscle and promoting satiety. While these trends are for humans, it turns out some birds also know how to add protein to their menu in unexpected ways.
Thanks to our incredible guides, Jhonny and Adrian, we discovered that parakeets can occasionally skip their usual seed-based diet and go for a protein-packed snack instead. During a morning walk in the Papagayo Peninsula, Guanacaste, we spotted an Orange-fronted Parakeet (Eupsittula canicularis) feeding on arboreal termites.
At first, we thought the bird was setting up a nest in the termitaria, as many species in the parrot family (Psittacidae) are known to do. But once we got the telescope in focus, it became clear: the parakeet wasn’t moving in — it was snacking on termites! Check out the footage to see this fascinating behavior in action.
Surprisingly, there are only a few documented reports of parrots feeding on insects, especially in the Neotropics. Two Brazilian studies, published in 1989 and 2007, highlight this unusual dietary behavior.
In the 2007 paper, Iubatã Paula de Faria wrote:
Parrots are rarely recorded feeding on insects. Forshaw (2006) reports on insectivorous habits for the genus Calyptorhynchus, an Australasian cockatoo, and New Zealand Nestor spp., regularly feed on insects. However, records are less scarce for Neotropical psittacids.
These observations provide valuable insights into the dietary flexibility of parrots, shedding light on behaviors that are likely underreported in the wild. What is better known, however, is how many parrots adopt termite mounds as nesting sites.
Take, for example, the stunning Golden-shouldered Parrot (Psephotellus chrysopterygius), an endangered species native to Cape York Peninsula, Australia, with only about 300 breeding pairs remaining. These parrots use giant termite mounds to dig their nests, taking advantage of the columnar termite towers to keep their nests cool — a clever adaptation to their environment.
Unfortunately, parrots nesting in termite mounds face a significant threat: they become easy targets for poachers. The conspicuous nature of these nesting sites, often located in open or easily accessible areas, makes them vulnerable to illegal harvesting. This is highlighted in a conservation field study on Yellow-faced Parrots (Alipiopsitta xanthops) in Paraguay, which documents how poachers exploit the visibility of termite mound nests to capture these birds.
Sexual selection: impressing the ladies
During our bird-watching hike with Jhonny and Adrian, we had the incredible thrill of spotting Long-tailed Manakins (Chiroxiphia linearis)! Long-tailed Manakins are stunning birds, with males boasting sky-blue backs, a bright red crown, and two long tail feathers that are twice the length of their bodies. These birds are famous for their elaborate courtship displays, known as lekking. Among manakins, the long-tailed species stands out for its highly coordinated and captivating performance.
Typically, two males (though occasionally three or four) team up to perform for a female. Perched on a branch, the males align in the same direction, facing their potential mate. The display begins when the first male launches straight into the air with a loud chirrup, hovering briefly before returning to the branch. While he is airborne, the second male edges closer to the female with a series of deliberate hops. As the first male lands behind the second male, the second male takes flight, mimicking the same upward leap and sound, while the first male hops closer. This precisely timed back-and-forth routine can continue for several minutes.
Interestingly, the lek includes males of varying social statuses: an alpha male, a beta male, and apprentice males. The alpha male leads the lek and is often the only one to mate if the female is impressed by the display. Alpha males can maintain their position for years, with beta males stepping up when the alpha dies. While the males demonstrate an intricate and cooperative social hierarchy, female manakins live mostly solitary lives, taking sole responsibility for raising offspring.
Other manakin species, such as the White-bearded Manakin, take courtship behaviors to even greater extremes. They have evolved a unique method of sound production, using their wings. By rapid muscle movements of their wings together mid-flight, they create a distinctive roll-snap-like popping sound to captivate females.
Another incredible tropical bird we encountered is the Montezuma Oropendola (Psarocolius montezuma). This bird is instantly recognizable by its striking golden tail feathers, which catch the sunlight as it flies — hence the name. But what truly sets this species apart is its elaborate mating ritual.
The male Montezuma Oropendola performs a dramatic courtship display to attract females, combining acrobatic movements with an extraordinary vocalization. As part of the ritual, the male hangs upside down from a branch, inflates its throat, and lets out a bizarre, gurgling call that sounds almost mechanical. This striking behaviour is a prime example of sexual selection, where features and behaviours evolve specifically to enhance reproductive success, even if they seem odd or impractical.
The golden tail feathers and unusual call are a testament to how evolutionary pressures can create traits that, while puzzling to us, are crucial for survival and reproduction in the natural world. The Montezuma Oropendola’s flamboyant courtship is just another reminder of how diverse and fascinating life in the tropics can be.
In The Evolution of Beauty, Richard Prum explores the evolution of courtship behaviours, questioning whether they are adaptive — enhancing offspring fitness — or if they follow their own evolutionary dynamics, a process known as runaway selection. He presents a compelling argument that female reproductive autonomy plays a central role in shaping male courtship behaviours. This autonomy can drive runaway selection, leading to the evolution of extreme and elaborate displays by males for the only purpose of impressing the ladies.
Beyond the spectacular displays of the Long-tailed Manakins and the Montezuma Oropendola, another equally mesmerizing example can be found in the intricate and artistic courtship rituals of bowerbirds. Male bowerbirds construct intricate bowers adorned with carefully chosen decorations, often favouring coloured objects arranged in precise patterns. Females assess these bowers and select a mate based on their perception of the male’s threat level, often gauging their ability to escape if they feel uncomfortable or unwilling to mate. This interplay between male displays and female choice highlights the profound influence of female autonomy on the evolution of courtship behaviours.
Bowerbirds, however, are found in New Guinea and Australia, so we’ll need to plan another trip to see them in the wild.
Whip spiders: hunting with your legs
Our guide Yajaira of the dry forest night tour pointed to the fascinating amblypygid Paraphrynus laevifrons. Made famous in the Harry Potter movies by the wizard Bartemius “Barty” Crouch Jr, it’s easy to see why this arachnid often appears on shows like Fear Factor — its size and the impressive pedipalps it uses to capture prey make it undeniably dramatic. However, Barty had an important detail wrong: these creatures are not lethal as he told his students; amblypygids do not possess venom glands and are harmless to humans.
Amblypygi is an order of arachnids colloquially known as whip spiders, though they are often referred to as tailless whip scorpions. This is confusing because there is also the whip scorpions or vinegaroons, which belong to a different order, Thelyphonida (also called uropygial to avoid further confusion). Thankfully, we learned to distinguish them during our exploration as whip scorpions can spray acetic acid and cause irritation. Vernacular names truly do matter.
What’s truly remarkable about whip spiders is their first pair of legs — an extraordinary example of exaptation, where a trait evolves to serve a new function. Unlike other arachnids, the front legs of whip spiders are highly specialized and function as sensory organs rather than for walking. These antennae-like legs are thin and elongated, equipped with numerous sensory receptors, and can extend several times the length of their body.
Amblypygids are said to be blind, but we couldn’t confirm this — only a few commensal species seem to lack vision. What’s clear, however, is that they rely heavily on their sensory legs to navigate their surroundings, detect prey, and strike with precision. Even more fascinating, they use these legs for social communication, such as during mating rituals and possibly in caring for their young. Weird-looking spiders that “talk” to each other through their legs? How cool is that!
Tiger beetles: walking on stilts
On the Pacific coast beaches of Costa Rica, we encountered one of our favorite insects: tiger beetles (Cicindelidae). These beetles are incredibly diverse in form and color, making them a delight to observe. Their agility and striking appearance never fail to impress.
Back in the 1990s, we’ve spent time studying these fascinating creatures, including recording some Australian species as the fastest-running insects — both in absolute speed and relative to their body size. Watching them dart across the dry salt lakes of Southern and Western Australia, it’s easy to see why they’re such a thrill for entomologists and nature lovers alike.
These Australian beetles possess unique adaptations that enable their remarkable speed, most notably their long, muscular legs. On the Costa Rican beaches, we encountered another species with similarly long legs: Opilidia macrocnema. This beetle also stood out for its elongated legs; however, unlike the Australian beetles, it was a relatively sluggish runner, and its long legs didn’t seem to provide any particular advantage in speed compared to other species. Instead, the long legs may represent an adaptation to the beach environment, perhaps allowing the beetle to “stilt” and remain elevated above the scorching sand, thereby reducing heat absorption.
Back in 2014, on the island of Borneo, Malyasia, we observed another beach-dwelling tiger beetle with very long legs: Abroscelis tenuipes. This beetle also didn’t appear to be an exceptionally fast runner, and it’s tempting to speculate that its long legs, like those of Opilidia macrocnema, are an adaptation to staying elevated above the scorching sand. Check how high it’s keeping its body above the hot beach sand in the photo above.
The tiger beetles we saw on the beaches of Costa Rica and Borneo belong to distinct branches of the tiger beetle evolutionary tree and are a nice example of convergent evolution. Both beetle species independently evolved long legs to adapt to their tropical beach environments and the scorching hot sand. Convergent evolution occurs when unrelated species develop similar traits to adapt to comparable ecological challenges. It would be amazing to find out what mutations enabled these beetles to convergently evolve long legs.
A classic example is the evolution of wings in bats, birds, insects and pterosaurs — each evolved the ability to fly independently. Similarly, cacti in the Americas and euphorbias in Africa have evolved strikingly similar shapes and water-storing tissues to survive in arid desert conditions, despite being unrelated plant families.
From a clambering cactus to a fruit for the 21st century
We often associate cacti with deserts, but these incredible plants have also evolved to thrive in tropical forests, blending seamlessly among other vegetation. The Guanacaste dry forests are particularly known for their cacti. Among them, the columnar Stenocereus aragonii stands out as the only native columnar cactus in the country and is endemic to the region. Reaching heights of up to 7 meters, it can be quite dominant amidst the tropical trees.
However, the cacti that intrigued us the most were the Hylocereus species — the night-blooming cacti also known as Selenicereus — which grow in the Guanacaste forests as viny epiphytes. These fascinating plants scramble over the vegetation using their stems and aerial roots. The technical botanical term for this behavior is “clambering,” in contrast to “climbing” plants, which use specialized structures to grip onto supports.
According to the Missouri Botanical Gardens Manual de Plantas de Costa Rica, there are four species of Hylocereus in the country. But then again, the genus Hylocereus turned out to be nested within Selenicereus, so all the species of Hylocereus were transferred a few years ago to Selenicereus. Give it to molecular taxonomists to casually rename genera and cause confusion: #deathbytaxonomy.
Our guide lamented that much of the cactus biodiversity of Costa Rica has been exported illegally, providing little benefit to the country. Indeed, you’ve likely encountered Hylocereus/Selenicereus fruits as dragon fruit, pitaya, or pitthaya. This is now a popular and expanding fruit crop that we can even find in some European supermarkets. Commercial cultivation of dragon fruit began in earnest in Southeast Asia and Central America in the 20th century, driven by its exotic appeal, vibrant color, and unique flavor. Its popularity has since skyrocketed, with markets across North America, Europe, and Asia embracing it for its health benefits and culinary versatility. Importantly, Hylocereus thrives in arid conditions, making it an ideal crop for agricultural systems grappling with the drier climates and water scarcity brought on by climate change. The crop is becoming established in dryland countries like Egypt, Tunisia and Saudi Arabia.
The local species, Hylocereus (aka Selenicereus) costaricensis, which is possibly the one we observed in the wild, produces fruits with red flesh. These fruits are rich in betalains, a group of powerful antioxidants responsible for the striking red/purple color. Betalains not only contribute to the fruit’s vibrant appearance but also presumably enhance its nutritional profile by offering anti-inflammatory and detoxifying properties, making dragon fruit a particularly healthful addition to modern diets.
Beyond leaves: how bark photosynthesis keeps trees thriving
Photosynthesis is a cornerstone of life on Earth, driving the energy flow that sustains nearly all ecosystems. This process, powered by sunlight, enables plants to convert carbon dioxide and water into glucose and oxygen. At its heart lies RuBisCO, the most abundant protein on the planet, responsible for fixing carbon dioxide during photosynthesis.
Traditionally, photosynthesis is thought to occur primarily in leaves, where cells packed with chloroplasts capture sunlight. However, photosynthesis can also take place in plant stems and bark, though this phenomenon is less studied. In some plants, particularly those adapted to arid environments, stem photosynthesis plays a vital role. Desert plants like cacti and euphorbias heavily rely on their green stems for photosynthesis, as they often lack functional leaves or have highly modified ones, making stem photosynthesis their primary means of energy conversion.
What we discovered on our trip is that stem photosynthesis is also crucial in tropical plants, especially trees. As our guide, Jhonny López, explained, the Gumbo Limbo tree (Bursera simaruba) showcases this adaptation remarkably well. During the dry season, when the tree sheds its leaves and sunlight penetrates to the trunk and exposed roots, it switches to bark photosynthesis. This allows the tree to continue producing energy even in challenging conditions.
Check out the green photosynthetic bark in the reel below — it’s a vivid reminder of how versatile plants can be. Bark and woody tissue photosynthesis is a somewhat neglected research topic, perhaps because it has been viewed as an ancient relic dating back to the origin of land plants.
Eleinis Ávila-Lovera, an Assistant Professor at the University of Utah, has been shedding light on this fascinating process. Her research highlights how carbon fixation in green stems serves as a vital energy source not only for succulents and cacti but also for plants that lose their leaves for part of the year. Stem photosynthesis plays a crucial role in helping plants survive in challenging environments, such as drought. In the face of the climate change crisis, this underappreciated process deserves much more attention.
Pochote tree: titans with thorns
Walking through the dry forests of Guanacaste, it’s impossible not to be struck by the sight of towering 50-foot trees, their trunks sheathed in an array of formidable large stubby thorns. These thorny giants are not only visually arresting, but they also hold captivating clues about their evolutionary history and their essential role within the ecosystem.
The Pochote tree (Pachira quinata), an iconic species of Costa Rica’s Guanacaste region, retains its spines throughout its lifespan. These sharp defenses are thought to be anachronistic relics from the Pleistocene era, when giant herbivores like megafauna, sloths, and gomphotheres roamed the landscape. While these ancient creatures are long extinct, the Pochote still carries the defensive traits that once protected it — a fascinating testament to its evolutionary journey.
Today, the Pochote has adapted to play a crucial role in Costa Rican agriculture. Its thorn-covered trunk forms an effective living fence, deterring livestock and acting as a natural barrier. In addition, its sturdy, termite-resistant wood is highly valued for sustainable furniture and construction, further enhancing its ecological and economic significance.
Incidentally, thorns and spines have distinct meanings in plant biology. Thorns are modified branches or stems that grow from shoot tissue, often emerging from axillary buds. In contrast, spines are modified leaves, stipules, or parts of leaves. Cacti, for instance, have spines (modified leaves), not thorns. Tree thorns and the spines that occur in many other plants serve as a vivid reminder of the remarkable ways plants evolve to thrive in ever-changing environments. In Costa Rica, these thorn-covered titans stand as both natural marvels and invaluable resources for local communities, providing both hardwood and functional fences.
Acknowledgements
We are grateful to the local experts who guided us throughout the trip: Yajaira, Jhonny, Adrian, Luis and Stefani and others who gave helpful tips or shared their experience. This article was written with assistance from ChatGPT.
Photo gallery
Here is a selection of some of our best photos from the trip. All shots were taken in late December 2024.
