The Galápagos archipelago, a chain of islands in the Pacific Ocean about 600 miles off the coast of Ecuador, is like no other place on earth. More than a hundred islets, rocks and 13 main islands make up the Galápagos. It is home to strange creatures found nowhere else. This is one of the few places in the world where you can scuba dive and snorkel with animals which remind one of the dinosaurs of ages past.
Steve Rosenberg is a widely-published, award-winning American underwater photographer and photo journalist based in California who has authored over 20 destination guidebooks for international publishers including Lonely Planet, Cruising Guides and Aqua Quest Publications.
He won more than 250 awards for his imagery in international competitions, including gold medals in the prestigious Hans Hass Photo Competition in Austria and the First World Underwater Photography Competition held in the Turks and Caicos Islands in 1997.
He holds the coveted SSI Platinum Pro 5000 certification, awarded to divers with 5,000 or more dives, and is founder of Dive Galápagos, which provides a complete guide to dive sites in the Galápagos Islands, as well as Rosenberg Ebooks, which produces interactive e-books for dive and travel guides.
¹ Shepherd, SA, and MW Hawkes. (2005). Algal food preferences and seasonal foraging strategy of the marine iguana, Amblyrhynchus cristatus, on Santa Cruz, Galápagos. Bulletin of Marine Science. 77 (1): 51–72.
The marine iguana (Amblyrhynchus cristatus), found only in the Galápagos Islands, is a marine reptile that closely resembles the movie adaptation of Godzilla. It has the unique ability among modern lizards to forage for food in the sea. These iguanas have spread to all the islands in the archipelago, living mainly on the rocky shorelines around all of the islands.
The ancestors of marine iguanas were probably a species of land lizards. The marine iguanas range in size from eight to 14 inches. They are not very agile on land, but are incredibly graceful swimmers. The subspecies of the marine iguanas in the archipelago are identifiable by their sizes as well as distinct colorations. For example, the Espanola subspecies is redder while the Santiago iguanas are greener. The iguanas found on Fernandina and Isabela islands are the largest iguanas that can be found in the Galápagos.
One of the best dive sites to interact with and photograph marine iguanas underwater is Cabo Douglas, located at the northeastern corner of Fernandina Island on the western side of Isabela. The Humboldt current is the predominant current in this area, bringing in nutrient-rich, but very cold water from the west. Temperatures frequently dip to a chilly 13°C (56°F). The Iguanas at this location often let divers approach very close, seemingly unconcerned by their presence, because they are concentrating on finding rocks covered with tasty algae.
Like all iguanas, they take on the temperature of their surroundings. In the chill of the early morning hours of the day, they can hardly move until the heat of the sun speeds up their metabolism. Galápagos marine iguanas are active during the day. In order to raise their body temperatures as much as possible, they will spend the first few hours after sunrise preparing for their dip in the ocean. The mostly darker colors of the iguanas allow them to rapidly absorb heat. In the morning hours; they can be seen sunning themselves on the shoreline or piled together to share heat.
The vast majority of individuals in each colony will wait until low tide and then feed almost exclusively on marine algae on exposed rocks in the intertidal zones. The largest males, making up only five percent of the population, have a bolder feeding strategy and will actually dive deeper into the water for food, and mostly during the hot midday hours. They will usually enter the water just before noon after they have had the opportunity to raise their body heat and will stay in the water to feed for up to two hours.
The best time to dive with marine iguanas is from 11:00 am to 1:00 pm when most animals can be found in the shallows. You can often expect to encounter many iguanas in the protected cove just to the east of the point at Cabo Douglas, on Fernandina Island, on the western side of Isabela. The waters in this area are extremely cold, fed mostly by the Cromwell Current, which brings nutrient-rich water from the deep ocean to the west. These chilly currents cause the iguanas to lose heat rapidly when feeding. This forces them to return to the rocks and warm up in the sun again after feeding.
Physical traits and behavior
The physical structure of these animals assists foraging. According to Shepard and Hawkes, the marine iguanas have “long claws, tough skin, blunt heads, flattened tails, and well-developed salt glands.” ¹ They have a laterally flattened tail and spiky dorsal fins, which aid in propulsion in the water and make them strong swimmers. The flat snout and sharp teeth enable them to graze on algae growing on rocks.
An iguana’s size and the way it retains or loses heat determines its method of feeding. Small individuals, which lose heat quickly, forage on rocks at low tide, scraping algae off the surface of the rocks, and they rarely dive into the sea. Larger individuals, however, do not lose as much heat and so they can be active for a longer period. They most often graze on algae in the shallow water at depths of two to five meters, but can dive up to 25m down to rocks where there is an abundance of green and red algae, and little if any competition from other iguanas.
Activity slows between noon and late evening. Around two pm, it appears as if someone has rung a signal bell, starting a stampede of iguanas back to the shoreline. Before sunset, the iguanas retreat into crevices or beneath boulders to spend the night.
Planning your dive
Divers who are interested in close encounters with these fascinating animals should select dive yachts that include Cabo Douglas on their itineraries. Plan your dives so that you are in the water before noon. It is not unusual to encounter 10 or more iguanas on a single dive.
Be patient and approach the iguanas slowly to get a closer look. When these animals are feeding, they do not seem too concerned by the presence of divers. As they cling tenaciously to the rocks, they can frequently be seen turning their heads to one side or the other, allowing them to harvest the algae with their rows of teeth on the side of their mouths. Their long, sharp claws keep them anchored to the bottom, allowing them to hold tightly onto rocks, helping them stay in one place and feed even in rough seas.
They can hold their breath up to 15 minutes and remain in the cold water for long periods of time. Once back on land, they can often be observed sneezing and expelling liquid from their nostrils. Marine iguanas take in toxic amounts of salt while feeding underwater. A nasal gland filters excess salt ingested while eating. This is expelled through the nostrils by snorting, often leaving white patches of salt on their face. They have adapted so well to the ocean that they have become the only sea-going lizards on the planet. ■
Download the e-book guide, Dive Galápagos 2nd Edition, for more information about marine iguanas and other fascinating creatures to be found in the Galapagos. You can find Dive Galápagos on iTunes, Google Play or Amazon, or for direct links to download the book from iBooks, Google Play or Kindle. For more information, go to RosenbergEbooks.com.
Visiwa vya Galapagos, vilivyo katika Bahari ya Pasifiki, vilivyo karibu na pwani ya Ecuador, ni sehemu ya ulimwengu. Visiwa hivyo vingi vina vilele vya miamba na vilele 13 vya majani, na vinaitwa Galapagos. Ni makao ya viumbe wa ajabu wasiopatikana mahali pengine popote. Hii ni moja ya maeneo machache duniani ambapo unaweza scuba dive na snorkel na wanyama ambao kukumbusha moja ya dinosaurs ya enzi zilizopita. Steve Rosenberg ni mchoraji wa picha wa chini ya maji wa Amerika na mwandishi wa picha anayeishi California ambaye ameandika zaidi ya vitabu 20 vya mwongozo wa marudio kwa wachapishaji wa kimataifa, pamoja na Lonely Planet, Cruising Guides na AquaQuest. Alishinda tuzo zaidi ya 250 kwa picha zake katika mashindano ya kimataifa, ikiwa ni pamoja na medali za dhahabu katika Mashindano ya picha ya Hans Hass ya kifahari huko Austria na Mashindano ya kwanza ya Dunia ya Upigaji picha chini ya maji yaliyofanyika katika Visiwa vya Turks na Caicos mnamo 1997. "Mwanzoni mwa miaka ya 2000, Rosenberg alipata cheti cha ""SSI Platinum Pro 5000"" na kuanzisha ""Dive Galapagos,"" ambayo hutoa mwongozo kamili wa maeneo ya kupiga mbizi katika Visiwa vya Galapagos, na Rosenberg Ebooks, ambayo inazalisha vitabu vya kielektroniki vya majaribio ya kupiga mbizi na kuongoza safari." 1 Shepherd, SA, na MW Hawkes. (2005). Mapendekezo ya chakula cha mwani na mkakati wa kutafuta chakula wa msimu wa iguana ya baharini, Amblyrhynchus cristatus, huko Santa Cruz, Galápagos. Gazeti la Sayansi ya Bahari. (Mstari wa 77): 51 <!> 72 "Iguana wa baharini (Amblyrhynchus cristatus) ni aina ya mnyama anayeitwa ""Godzilla"" ambaye anaishi katika visiwa vya Galapagos." Ina uwezo wa pekee miongoni mwa mbawakawa wa kisasa wa kutafuta chakula baharini. Iguana hao wametokea katika visiwa vyote vya kisiwa hicho, na wanaishi hasa kwenye pwani zenye miamba. Yaelekea babu za iguana wa baharini walikuwa spishi ya mbawakawa wa nchi kavu. Iguana wa baharini wana ukubwa wa inchi nane hadi kumi na nne. Wao si wepesi sana kwenye nchi kavu, lakini ni waogeleaji wenye ustadi sana. Spishi ndogo-ndogo za iguana wa baharini katika visiwa hivyo zinaweza kutambuliwa kwa ukubwa wao na vilevile kwa rangi zao tofauti. Kwa mfano, spishi ndogo ya Espanola ni nyekundu zaidi ilhali iguana wa Santiago ni kijani-kibichi zaidi. Iguana wanaopatikana kwenye visiwa vya Fernandina na Isabela ndio iguana wakubwa zaidi wanaoweza kupatikana katika Galápagos. Moja ya maeneo bora ya kupiga picha ya iguana chini ya maji ni Cabo Douglas, kwenye kona ya kaskazini mashariki ya kisiwa cha Fernandina upande wa magharibi wa Isabela. Mtiririko wa Humboldt ndio mkondo mkubwa katika eneo hili, ukileta maji yenye virutubisho vingi, lakini baridi sana kutoka magharibi. Mara nyingi joto hupungua hadi digrii 13 C (56 F). Iguana katika eneo hili mara nyingi huruhusu waogeleaji wakaribiane sana, wakionekana kuwa hawajali uwepo wao, kwa sababu wanakazia fikira kutafuta miamba iliyofunikwa na mwani wenye ladha. Kama iguana wengine wote, wao huathiriwa na hali ya joto ya mazingira yao. Katika baridi ya asubuhi, hawawezi kusonga mpaka joto la jua lifanye kazi kwa kasi zaidi. Iguana wa baharini wa Galápagos huishi wakati wa mchana. Ili kuongeza joto la mwili wao, wao hutumia masaa machache ya kwanza baada ya jua kuchomoza kujiandaa kwa ajili ya kuoga katika bahari. Rangi nyeusi zaidi za iguana huwaruhusu kuvuta joto upesi. Katika saa za asubuhi; wanaweza kuonekana wakichukua jua kwenye pwani au wakiwa wamekusanyika pamoja ili kushiriki joto. Watu wengi katika kila koloni watangoja mpaka wakati wa maji kupungua na kisha kula tu mwani wa baharini kwenye miamba iliyo wazi katika maeneo ya kati ya maji. Wanaume wakubwa zaidi, ambao ni asilimia tano tu ya idadi ya watu, wana mkakati wa kulisha wenye ujasiri na kwa kweli wataingia ndani zaidi ya maji kwa chakula, na hasa wakati wa saa za joto za mchana. Kwa kawaida huingia majini kabla ya adhuhuri baada ya kupata nafasi ya kuongeza joto la mwili na kukaa ndani ya maji ili kula kwa muda wa saa mbili. Wakati mzuri wa kupiga mbizi na iguana wa baharini ni kati ya saa 11 asubuhi na saa 1 jioni wakati wanyama wengi wanaweza kupatikana katika maji ya chini. Kwa mfano, kuna aina ya iguana inayoitwa iguana ya mto wa Isabela, ambayo hupatikana karibu na Cape Douglas, kisiwa cha Fernandina, upande wa magharibi wa kisiwa hicho. Maji ya eneo hili ni baridi sana, na yanaendeshwa hasa na Mtiririko wa Cromwell, ambao huleta maji yenye virutubisho kutoka baharini kina kirefu kuelekea magharibi. Mtiririko huo wenye baridi hufanya iguana hao wapoteze joto haraka wanapokula. Hilo huwafanya warudi kwenye miamba na kupasha joto tena jua baada ya kula. Sifa za kimwili na tabia Muundo wa kimwili wa wanyama hao husaidia kutafuta chakula. Kulingana na Shepard na Hawkes, iguana wa baharini wana "madoa marefu, ngozi ngumu, vichwa visivyo na umbo, mikia iliyo tambarare, na tezi za chumvi zilizoendelea vizuri". 1 Wana mkia ulio tambarare upande mmoja na mabawa ya mgongo yenye miiba, ambayo husaidia kusukuma katika maji na kuwafanya wawe waogeleaji wenye nguvu. Mdomo wake ulio tambarare na meno yake makali huwawezesha kula mwani unaokua kwenye miamba. Ukubwa wa iguana na jinsi anavyohifadhi au kupoteza joto huamua jinsi anavyojilisha. Watu wadogo, ambao hupoteza joto haraka, hutafuta chakula kwenye miamba wakati wa mawimbi ya maji, wakikokota mwani kutoka juu ya miamba, na ni nadra sana kupiga mbizi baharini. Hata hivyo, viumbe wakubwa hupoteza joto kidogo na hivyo wanaweza kuwa hai kwa muda mrefu zaidi. Wao mara nyingi hula mwani katika maji ya chini ya mita mbili hadi tano, lakini wanaweza kupiga mbizi hadi mita 25 chini ya miamba ambapo kuna wingi wa mwani wa kijani na nyekundu, na ushindani mdogo kutoka kwa iguanas wengine. Shughuli hupungua kati ya adhuhuri na jioni sana. Karibu saa mbili mchana, inaonekana kana kwamba mtu fulani amepiga kengele ya ishara, na kuanzisha mkondo wa iguana kurudi kwenye pwani. Kabla ya jua kutua, iguana hujificha katika nyufa au chini ya miamba ili kulala usiku huo. Kwa wale wanaopenda kupiga mbizi na wanyama wa ajabu, ni bora kuchagua boti za kupiga mbizi ambazo zina Cabo Douglas kwenye njia zao. Panga kupiga mbizi zako ili uwe ndani ya maji kabla ya adhuhuri. Ni kawaida kuona iguana kumi au zaidi katika safari moja ya kupiga mbizi. Uwe na subira na ufikie iguana polepole ili uone kwa karibu zaidi. Wanyama hao wanapokuwa wakila, hawaonekani kuwa na wasiwasi sana kuhusu kuwapo kwa wapiga-mbizi. Wanaposhikamana kwa nguvu na miamba, mara nyingi wanaweza kuonekana wakigeuza kichwa chao upande mmoja au mwingine, na hivyo kuweza kuvuna mwani kwa kutumia safu zao za meno upande wa kinywa chao. Mikono yao mirefu na mikali huwaweka chini ya maji, na hivyo huweza kushikamana kwa nguvu na miamba, na hivyo kukaa mahali pamoja na kula hata wakati wa bahari yenye msukosuko. Wanaweza kushikilia pumzi kwa dakika 15 na kukaa ndani ya maji baridi kwa muda mrefu. Wanaporudi ardhini, mara nyingi wanaweza kuonekana wakitokwa na chafya na kutoa umajimaji kupitia pua zao. Iguana wa baharini huchukua chumvi nyingi zenye sumu wanapokula chini ya maji. Tambo ya pua hufuta chumvi nyingi inayomezwa wakati wa kula. Hii hutolewa kupitia pua kwa kunyonya, mara nyingi ikiacha madoa meupe ya chumvi usoni mwao. Wamejipatanisha vizuri sana na bahari hivi kwamba wamekuwa mbawakawa pekee wanaoweza kwenda baharini duniani. "Kuchukua kitabu ""Dive Galapagos 2nd Edition"" na kufurahia uzoefu wa kuogelea katika Galapagos." Unaweza kupata Dive Galapagos kwenye iTunes, Google Play au Amazon, au kwa viungo vya moja kwa moja kupakua kitabu kutoka iBooks, Google Play au Kindle. Kwa habari zaidi, nenda kwenye RosenbergEbooks.com.