Saltwater Crocs and Marine Iguanas

         Saltwater crocodiles, or “salties”, as Australians call them, are carnivorous reptiles that can live up to 70 years in the wild. Their main predating method is drowning their prey. In the kingdom of Animalia, phylum Chordata, class Reptilia, genus crocodylus, and species Crocodylus porosus, its 5 meter long body can weigh up to 450 kilograms, or 17 feet and 1,000 pounds. Meanwhile, Marine Iguanas, in the same kingdom and phylum as the salties, are in class Saropsoda, and genus Amblyrhynchus. It has one known species, named Amblyrhynchus Cristatus. The Marine Iguana really only has one name- “Marine Iguana”. Saltwater crocodiles have a wide variety of common names, such as “salties”, “Estuarine Crocodile”, “Australian Saltwater Crocodile”, or “Rawing crocodile”. Marine Iguanas, compared to Saltwater Crocodiles, are relatively tiny. The average male will only span up to .75 meters, and weigh up to 1.5 kilograms, while females span up to .6 meters and weigh about .5 kilograms.

         Marine iguanas in the Galapagos are the only marine lizards in the world. After a cursory glance, they may seem like any other lizard, but they actually have blunt noses and vertically flattened tails, alongside powerful limbs and strong claws. Their size determines their feeding habit, as these iguanas need to stay warm, so smaller iguanas stay on shore and forage for algae off of rocks, while larger iguanas will dive into the sea to either graze on algae in the water’s shallows or go down deep to the rocks on the bottom, where there is little competition from other iguanas. They tend to mate in December or January, when their normally greyish-black dorsal scales sometimes have coppery green or red splotches on them, from eating a specific kind of seaweed in the summer. Adult males and females can be easily be distinguished from each other, because males are much larger than females; however, when the scales are darker than usual, it is because the iguana is a juvenile. Contrarily, saltwater crocodiles are one of the largest crocodile species, and the world’s largest living reptile going by mass. Its heavy jaws of 64-68 teeth means that it can eat many different sorts of prey, and large adults can successfully attack and consume much bigger prey, like the wallaby. These crocodiles also tend to mate at the end of the year, around November, when both the male and female are mature. For the males, this happens when they are approximately 3.2 meters long or 16 years old; females mature earlier, when they are around 2.2-2.5 meters long or 10-12 years old. Interestingly enough, the temperature at which their eggs are kept determines their sex. Males turn out when their eggs are kept at a temperature of approximately 31.6°C, and females are born at any temperature slightly above or below that. The scales on the saltwater crocodile’s flank are typically oval in shape; however, the scales on the belly are rectangularly even and small. Mature crocodiles have a darker coloration on the dorsal side, with the occasional tan or gray area, while the ventral side has a creamy yellowy-white color, until the the tail, which is grayer, towards the tip. The lower part of the upper abdomen has dark stripes or bands, and sometimes, there will be two dark spots on the belly, but would be considered rare.

         The typical marine iguana starts out its day with some sunbathing on the volcanic rocks at the edge of the Galapagos Islands. Since the iguana is cold-blooded, the sunbathing helps it to function better in the day, because this action warms up the iguana’s body, especially because the dark lava rocks attract plenty of heat for the iguana to soak up. Its history is long- having been around for 10 to 15 million years. It is thought that it came from South America, and after all these years, is now considered vulnerable to being extinct. Even though there have been laws that are supposed to help prevent this possibility of extinction from occurring, natural predators, like feral dogs, cats, and rats still eat these iguana eggs and iguanas. In addition, the 1982-1983 El Nino had huge detrimental effects on the iguana population- the environment’s fluctuations and a weird alga invasion that the iguanas couldn’t eat killed pretty much half the population. Then, in 2001, an Ecuadorian oil tank spill killed approximately 15,000 iguanas, because it is thought that the oil killed a bacteria that helped the iguanas’ bodies digest nutrients. While the number of iguanas did drop, since iguanas have the ability to increase reproduction rate when the population density is low, the numbers didn’t fluctuate too much. Also, another unique characteristic of these iguanas is their ability to either shrink or expand, according to the amount of food it consumes. Not only does it become fatter or skinnier, but it can also become longer or shorter.

         A recent study of saltwater crocodiles has revealed that oxidative stress during development may be related to the seasons. The oxygen breaks down the lipids in the crocodile cells, which cause them to slowly degrade. However, this phenomenon only occurs in the hatchling to juvenile stage, not the juvenile to adult stage. The conclusion of this experiment was that the differences in levels of oxidative stress in these saltwater crocodiles were affected by the temperatures of the nocturnal temperatures of the summer-winter seasons.

         Marine iguanas and saltwater crocodiles are both water loving creatures. However, the crocodile is much more feared than the iguana is. While, in truth, they shouldn't be feared as much as they actually are, they can still be slightly dangerous, just not directly to humans. Baby crocodiles enjoy eating little insects, amphibians, crustaceans, fish or smaller reptiles. Adult "salties" are more partial to eating livestock and animals than they are to eating actual humans. They also eat what the babies eat, just in larger proportions. Marine iguanas are mainly herbivorous, they eat algae from rocks, and the larger iguanas will dive down to the water's bottom, to feed off the rocks on the bottom. The smaller iguanas don't dive, because the water is too cold for them and this makes their body temperature too low. Larger iguanas don't lose as much body heat as quickly as smaller iguanas do, so they do the diving. Crocodile genders are determined by the temperature at which the nest was kept. In both species, the female will guard the unborn eggs, but out of the two, the marine iguana is the most territorial and protective of the eggs. Marine iguanas have a strange phenomenon. When they don't eat for an extended period of time, they not only become thinner, but they also become shorter. Marine iguanas are actually considered vulnerable to extinction. While there are laws in countries such as Ecuador protecting these iguanas, there are still many natural threats these iguanas face. The future of the crocodile species looks to be rather secure for now, since Australia and Papua New Guinea seem to have a large population of them; yet in some places where the management programs aren't as effective, its range can be drastically lessened. While both of these species are unique, they do share some of the innate characteristics of reptilian animals. These crocodiles, while not completely harmless, are still wild animals, so as with all wild animals, people need to be careful around them.