Week Ending 11th December 2015
Average High Temp 101ºF (38.3ºC) Average Low Temp 75ºF (24.3ºC)
Average Rainfall 1 ins (25.4mm) Total Rainfall 7 ins (177.8mm)
Wet and Dry
The dry season at Bosque del Cabo Rain Forest Lodge always experiences a stuttered beginning. The lodge is located on the south west tip of the Osa Peninsula, Costa Rica overlooking the Pacific Ocean to the south and the Golfo Dulce to the east. The region is covered by some of the last remaining tropical forest on the Pacific Coast of Central America. Due to the pronounced seasonality of the area having a profoundly dry five months followed by a wet seven months the forests here are more correctly classified as tropical seasonal forests as opposed to tropical rain forests which are not subject to the annual dry period.
The heaviest rains of the year fall between September and November. By December the daily deluge abates and we gradually see more of the sun. It is easy to be lulled into a false sense of “the summer is here” as commonly a few dry, bright days with blue skies will be followed by another week of torrential downpours. But eventually the faltering weather passes through the transitional phase and settles into a more predictable pattern. Given a few weeks of steady, dry heat and the plant life will begin to flower. The number of butterfly species and individuals that had dropped in the wet season begins to build once more so the days are now filled with beautiful, brightly colored wings adorned in poster reds, yellows and orange dancing around the flower heads.
There is never a shortage of mammal or bird sightings. Currently there are many migratory warblers and tanagers chattering noisily in mixed flocks as they move from tree to tree in search of insects or fruit to eat depending on their specific diet. The resident bird populations do not mind those long distance travelers returning to spend the winter in the warmer climes of the tropics and join quite readily with their travelling cousins in large flocks. Monkeys abound in the trees, constantly on the move looking for food whether it is flowers, young leaves, fruit or insects. Under the trees the large ground living rodents, Agoutis, feed on the fallen fruit and large heavily coated seeds. Solitary male White-nosed Coatis are on the lookout for anything they can get their paws on; grubs, crabs, bird’s eggs and chicks as well as fruit or discarded food in the bins of the restaurant. The gregarious females with young patrol in large foraging packs looking for the same food as the males but not with the same bold abandon.
The peace of the hot still sultry afternoon atmosphere is occasionally permeated by the call of a mammal or bird. The ever active Spider Monkeys let out a series of high-pitched shrieks which sporadically turn into a hysterical frantic screaming match. From deep in the forest the doleful Howler Monkeys bark and roar their disapproval of some irritation. The White-faced monkeys oblivious to the presence of human observers chitter and chatter amongst themselves. Coming from the surrounding vegetation are the chirps and cheaps of the warblers and tanagers. But for the most part the soporific pulsating heat and the throbbing silence serve to create a languid attitude for visitors to the tropics.
All of a sudden the siesta is interrupted by a harsh ear-piercing screech. Several birds of prey inhabit the area and neither the hawks nor the falcons have been blessed with a melodious call. Commonly seen sitting at the top of the palms or on the ground are the Yellow-headed Caracaras, (Milvago chimachima). Despite their raptorial appearance these elegant members of the falcon family are generally carrion feeders. They can also be seen riding the backs of cattle feeding on bovine ticks. Due to their association with cattle they are commonly seen in open pastureland. Until 1973 they had not been recorded in Costa Rica but following widespread deforestation their distribution and geographical range spread north from Panama into Costa Rica and they can now be seen in Nicaragua.
That nasty nasal screech was an adult Yellow-headed Caracara calling from on the ground but there was another call, similar yet more urgent. Not too far from the adult was a newly fledged youngster that was making its first foray from the nest. It had not yet mastered the art of flight and was demanding food from the parent bird that was watching warily over its offspring’s pitifully laborious progress hopping and jumping across the ground. The brown speckled shabby looking youngster bore little resemblance to its sleek yellow-faced dark-browed parent standing guard over its precarious and vulnerable position.
From Sublime to Ridiculous
Another bird seen either high or low is the Turkey Vulture, (Cathartes aura). As you look up into the deep blue tropical sky it is likely that you will see flocks of birds soaring on the thermals. Silhouetted against the azure background the shapes and shades circling above you will help discern the different species present. Long thin wings bent back from the center like a Batman motive combined with a forked tail easily characterize the Magnificent Frigatebird. A huge bird with broad, wide wings fingered at the end and divided into a monochrome white leading edge and black trailing edge leave no mistake that this is a King Vulture. Similar in shape but uniformly dark except for grey fingered tips is the Black Vulture. Soaring with them with the same wing form but with longer tail and complete grey trailing edge is the Turkey Vulture.
On the ground there is no mistaking the Turkey Vulture for its head bare of feathers is bright red. Like the Yellow-headed Caracara the Turkey Vulture feeds on carrion but unlike its falcon cousin which locates food visually, the vulture has a highly developed olfactory sense and can locate the chemical signature of decomposition following the plume of molecules of death to their source hidden beneath the forest canopy. They can often be seen beneath the palm trees feeding on the fallen palm fruit.
Vultures are not everyone’s favorite bird but they play a vital ecological role in disposing of rotting carcasses and rubbish that won’t make to a landfill site.
Fruit and Nuts
Sitting beneath the palm trees in the company of vultures one will more often than not see Agoutis, (Dasyprocta punctata). These large ground living rodents are related to Capybaras, Coypus, Pacas and more familiarly Guinea Pigs. Along with the vultures they are waiting for the palm nuts to fall. Agoutis are essentially seed eaters and have the ability to sit back on their haunches while holding the seed in their front paws which they can manipulate and turn allowing them to easily gnaw through very tough seed coats such as nuts.
At the moment there are a lot of fruits on the grapefruit tree which when ripe fall. Eagerly awaiting this softer option dropping from above there are some Agouti individuals that pick up the sizable citrus prize in their mouths and carry it off to be eagerly consumed. They do not eat the peel but rather the soft juicy segments inside.
Whereas during the day vultures and Agoutis can be seen frequenting the palm trees at night it is possible to see another creature that utilizes the palms. If you look a little more closely at what might seem like old and dropping palm fronds you will see that they will have had another force at work. Something has nicked through the veins of the frond to be point where it folds over. Take a look inside and there you will most likely find the culprit responsible for this chiropteran topiary – the Tent-making Bats, (Uroderma bilobatum).
The Tent-making Bats use the tents as either day roosts or night roosts. If they are using them as a day roost there can be as many as forty bats hanging under the frond. They regularly change the location of each roost they are using as predators would quickly figure out where to get an easy meal. One of the commonest predators of the tent making bats are the Squirrel Monkeys. During the day they identify which roosts are being used by the bats climb to the fronds above and then drop onto the roost. The startled bats come fluttering from underneath where they are picked off by the monkeys.
Currently they are being used as night roosts. Once the sun has set the bats leave the day roosts and fly to the selected night roosts where they wait until it is very dark before they go foraging for food. The Tent-making Bats are fruit-eating bats and use night roosts which are never more than 80 – 100 meters away from the nearest fruiting trees which in this area are figs. The carry the figs in their mouths back to the night roosts whereupon landing they then hold the fruit between their wings, peel off the skin with the teeth and eat the pulp. Just before the sun rises they leave the night roosts and return to the day roosts where they will pass the day sleeping.
Philip Davison is a biologist, writer and photographer based in Costa Rica.