Wednesday, August 23, 2017

Northern Watersnake

A Northern Watersnake basks in an Arlington, Virginia pond.

     The Northern Watersnake (Nerodia sipedon sipedon) may well be the most misidentified snake in the East. Due to its living in close proximity to water, large size, variable coloration, ability to flatten its heads to appear triangular, and what some consider a feisty nature, many people confuse it for the venomous Water Moccasin (Cottonmouth) snake. This despite cottonmouths actually not living in the DC area, being limited to Southern Virginia at most. 

A Northern Watersnake eating an American Eel it has dragged out of the water. Not the dark bands thickest along the top of the body.

     Northern Watersnakes are thick-bodied snakes, up to 55 inches in length (though most are 2-3 feet on average). They can have a wide range of color, and the tannins and mud in the water may also stain them. Most however have dark bands across their back that are wider than the light colored bands along their bodies. The dark bands narrow along their sides and thicken along the top of their backs. These bands tend to turn into blotches by the time they reach their tails. The bands also fade as they grow older, becoming difficult to see on the oldest and largest specimens. These snakes also have crescent-shaped marks along their bellies, but that is obviously not an easy thing to see.

Note the crescent-shaped marks along the belly of this watersnake. The tail is almost completely dark underneath.

     Watersnakes (all one word is the scientifically accepted way of spelling the name) are quite common, being found in every county in Virginia and almost all the DC area. They are almost always found in close proximity to water. They can swim completely submerged, which differs from many other types of snakes.

Juvenile Northern Watersnakes are more boldly patterned than adults. Note that the dark bands are wider than the light colored ones and that they are widest at the top of the back. This youngster is swimming submerged underwater. 

     Northern (also called Common) Watersnakes are diurnal, being most active during the day. They feed primarily on fish and amphibians, which are swallowed alive. They will however sometimes pull their prey out of the water and eat it after it has died, particularly if it is putting up a good struggle. They're also one of the few snakes who will eat carrion. Here is a video taken during our Arlington Bioblitz of a watersnake that has wrestled an eel out of the water to eat: 

     Because fish and amphibians are so slippery, watersnakes have very long and pointy teeth, pointing backwards to help hold on to prey. They also have a mild anticoagulant in their saliva. Since they will bite defensively, this can make a bite look scary, though the watersnake really can't do any real harm. The vast majority of the time they try and flee. If captured or cornered, they will flatten out to look bigger, hiss, strike, musk, and even discharge feces, so it's best if they're left alone. Some people report being attacked by them, but what has often happened is that the snake is trying to get to a burrow that the person is in front of, or trying to get aboard what they think is an island when it's someone canoe. They really just want to get somewhere and a person happens to be in the way. This unfortunately adds to the misconception that they're dangerous or aggressive however. 
     Female watersnakes are larger than males, sometimes twice the size. If you see a large one, it is almost certainly a female. This size difference allows them to be able to produce more young. From 6-70 (though 20 is more typical) young are born alive from eggs retained within the mother's body, often from August through October. The largest females produce the most young. Males are attracted to females, finding them by searching for pheromone trails. This sometimes result in "mating balls" of one large female surrounded by 2 or more suitors. If nothing happens to them (lots of things such as herons, raccoons, large fish, snapping turtles, foxes, and mink will eat them, specially when young), they can live up to 9 years and 7 months.
     Though these snakes can appear dangerous, they really just want to be left alone. They're fascinating creatures who are important predators in our waterways, when not serving as prey themselves to other wildlife. Here's one last look at one as it swims away, trying to avoid any confrontation:

Monday, June 19, 2017

National Pollinator Week: Pollinator Patches and Way Stations

A bumblebee, metallic sweat bee, and orange-spotted mint moth all feeding on a native green-headed coneflower in the native plant garden at Long Branch Nature Center.

     Happy National Pollinator Week! There are over 200,000 species of pollinators worldwide. These include such diverse animals as bees, wasps, butterflies, moths, flies, beetles, and hummingbirds. We owe them much, as it is often said that one out of every three bites of food we enjoy is due to the direct actions of an animal pollinator. In fact, three-quarters of all plants regardless of whether we eat them or not depend on animal pollinators in order to reproduce.
     When thinking about planting things to benefit our pollinators who benefit us so often, a critical thing to consider is the use of native plants. Studies show that native plants are four or more times more attractive to native pollinators than exotic plants. This, of course, makes perfect sense since these plants and animals evolved together, sometimes to the point that one cannot exist without the other. Many caterpillars for example cannot survive without their specific native host plant to feed on. About a third of our native bees need the specific pollen of certain native plants or they cannot reproduce. 
     So the most important consideration is to plant plants that are locally native. These plants are not only adapted to grow in this type of habitat, but are what the pollinators have been using for thousands of years. It is also always best to use straight wild species,rather than cultivars or nativars which have been selected for certain traits. When we plant a flower that has been bred to appeal to us through a novel color or look, it may not have the same appeal to the pollinator its parent plants originally evolved with. What might be attractive to us may not be attractive to pollinators, some of which see flowers through different spectrums or look for certain traits in them. This is especially true of plants bred to have double flowers or blooms with extra large petals, since they often sacrifice nectar/pollen for the extra showy flowers.
     Also something to consider are the multiple uses you get with native plants. Many exotic plants may have a pretty flower that may (or may not) provide nectar for a short time each year while blooming, but it otherwise provides little habitat or nutrition for pollinators or other native wildlife. Take the Chinese Aster (Callistephus) for example. It is a pretty flower, comes in many color forms and is widely planted (and has escaped and naturalized into some areas). The blooms on some varieties provide some nectar and pollen to a few pollinators for a short bloom time each year. But only two species of caterpillars have been recorded as feeding on it. It is for the most part and for most of its plant life a barren habitat for wildlife, taking the place of what might have been a much more beneficial native plant.
     Contrast that with one of our many (Virginia alone has 43 different species) colorful and attractive native asters, many adapted to a variety of growing conditions. Now you have flowers that not only provide attractive flowers for the garden and a similar look, but also serve a habitat and food function. In addition to pollinators visiting them, most also supply seeds for birds such as finches and sparrows. But 109 different caterpillar species have also been documented feeding on asters. These in turn feed the vast majority of our nesting native birds (97% of terrestrial birds feed on insects, particularly during the nesting season, most of which are caterpillars) and most of the 18 bat species found in our region (all of which are insectivores and many of which prefer moths over other insects). At least 8 different bee species need their pollen or they cannot reproduce.

A pair of Checkered Skippers feed on a native aster. 

     So you can see how something as simple as choosing a native plant species can not only serve to provide for pollinators, but then serve many other habitat functions as well. So this National Pollinator Week, enjoy the pollinators in our gardens, farms, and parks. If you're able to, include locally native plants in your gardens. This way you too can help the pollinators who are always helping us.
     In Arlington County, we try and make the vast majority of the plants we plant natives for all the reasons stated above. This National Pollinator Week we will be partnering with Dominion Energy to plant a Pollinator Patch in Bluemont Park featuring over 500 native plants. This will be one of several plantings we have made that we will try and certify as Monarch Way Stations. This week serves as the one year anniversary that Arlington County made the Mayor's Monarch Pledge to commit to doing several different things to help monarch butterflies. The milkweed plantings and meeting the rest of the pledge requirements will help us to certify this site among several as a wrap up of this year's efforts. We of course will continue to do many other things to help monarchs and and so many other pollinators. The establishing of Pollinator Patches and Monarch Way Stations is just one way we will continue to do so in to the foreseeable future. Please join us in supporting our pollinators by planting native plants when you can and taking pollinator needs in to consideration when you do things at home. 

A Monarch Butterfly and Clearwing Moth nectar at a native Swamp Milkweed flower in the Gulf Branch Nature Center Monarch Way Station and Pollinator Garden. 

Friday, May 26, 2017

A Kissing Bug - The Eastern Blood-sucking Conenose

An Eastern Bloodsucking Conenose - a Kissing Bug - found during the Arlington Bioblitz

     Among the neat finds made during the first ever Arlington Bioblitz in 2017 was made by one of our distinguished experts: former Smithsonian entomologist Warren Steiner. I've had the honor to be in the field several times with Warren, and he always makes some fascinating observations and discoveries. But they're usually in his specialty of beetles. This time around it was a true bug.
     Not just any bug mind you, but one with which I've had an interesting past with. He found what is known as Triatoma sanguisuga, formally called the Eastern Blood-sucking Conenose. But I knew it by another name when I first encountered it. My encounter happened several years ago in El Salvador.
     Since my wife's family is from El Salvador (she was born in Honduras however), I was on one of my extended visits. As her family lives in a very humble setting without a lot of the things such as running water one is often accustomed to, you do without a few creature comforts. You also are living among the chickens, ducks, dogs, cats and other regular household creatures who often share your hand-carved habitation. This also includes mosquitoes and other insects.
     The custom is then to use mosquito netting and run a fan. I had taken the normal precautions, but they did not deter a night time visitor, one that went under the mosquitero. I woke the next morning with the customary roosters calling, but with a greatly swollen lip. In fact, it was stiff as cardboard and even affected my speech. I had been "kissed" by a kissing bug!
     Kissing bugs are assassin bugs who have specialized their diet to include blood meals. There are various species throughout the Americas, including the Eastern Blood-sucking Conenose who it is believed ranges throughout the Americas. They in fact need a blood meal in order to lay eggs.
     Normally this is obtained from small mammals, but they will not pass up any blood meal they can, including humans. They are sometimes called Mexican Bedbugs. They often are attracted to moisture, such as from the edges of your lips, thus their common moniker of "kissing bugs."
     The one I encountered had decided to kiss me in my sleep. At the moment it happens, I can attest, you do not feel a thing. But later on you can get some sometimes serious reactions. Some folks get an allergic reaction. I was lucky it seems to just get a fat lip. But the most feared reaction is if you get infected with the incurable Chagas' disease.
     My own family is from Peru, where as in other parts of South America, it is possible to get infected by Chagas', something I was well aware of. So while every one else found a lot of humor in my huge cardboard-like lip and speech impediment, I was a bit concerned. Luckily for me, the South American kissing bugs are much more likely to infect you with the protozoa Trypanosoma cruzi which causes the illness.This is due to their feeding habit, where they often defecate onto the wound which increases the odds of transmission. The Eastern Blood-sucking Conenose does not do so and so has a much less chance of transmission. Lucky for me, as I just had to deal with the disfigured lip for the whole day, but the joking continued for much longer.
     So I was very surprised when Warren relayed that he had found one during the Bioblitz, showing it to me in a cup. I really had thought they were a Latin American thing. Instead they are more widespread, though more common in the South. It may very well have been the same species who snuck into bed with me to steal a kiss. I never thought I'd find another one around here, or that I'd kiss and tell...

Tuesday, May 16, 2017

Periodical Cicadas Early Emergence

A Periodical Cicada perched

     So the calls and emails have all been coming in. Some people happy and fascinated, others much more fearful, as they think that a great plague is about to strike. The emergence of dozens of cicadas has many people wondering what's going on. Some are aware of Periodical Cicadas, sometimes called locust in a reference to biblical invasions of insects, others are not. 
     Indeed, we are in the midst of an emergence of Periodical Cicadas, but not the natural phenomenon of a great cicada year. The Big One is not due until 2021. Cicadas are insects known for the loud songs of the males. While we have numerous species of annual cicadas that come out every year during summer (many of which take more than one year to mature, but they're staggered in breeding so some are out every year), Periodical Cicada are much different. 
     Periodical Cicadas (Magicicada species) emerge in huge numbers in late spring, generally on 13 and 17 year cycles. There are 7 Magicicada species, of which 3 are local to the DC area. They generally time themselves so they come out in gigantic numbers, thus the reference to biblical plagues of locust and their alternate name. By all coming out (and earlier in the season before predators like Cicada Killer wasps are active) at one time in such huge numbers, they make it impossible for all of them to be eaten. Though a favorite food, they just are too many to all get eaten. Since they come out after such an extended period of years underground, no single predator has adapted to feed on them exclusively. They just overwhelm all the potential hazards, so though thousands die, millions make it. 
     Since their emergence is synchronized over different regions, people have divided these regional  cycles into Broods. There were 23 different Broods recognized at one time, but some have gone extinct. The DC area is part of Brood X. 
     Periodical Cicadas spend the vast majority of their lives underground, usually either 13 or 17 years. The larvae feed for years on the roots of trees for the most part, sucking what they need to survive from them, molting into bigger larvae every year. Though that many feeding would seem to damage the trees, they rarely cause any real damage in this stage. Eventually their internal clocks go off, usually after the ground 8 inches down reaches 64 degrees Fahrenheit. Sunnier areas thus have them emerge before shadier ones. 
     The larvae (referred to as nymphs) somehow time their climb out of their burrows for the same year (mostly). Some get to the surface before others, but many may just wait until the rest are ready and stay underground, though their burrow entrances of pushed up soil, called turrets, may become noticeable.

Exit holes and a shed skin

     Those that are ready to emerge often wait until just after dark and then climb the nearest thing around them. This is usually a tree, but tall plants and even walls are fair game. They often have better success obviously on less slick surfaces such as rough barked trees. The nymphs climb until they get some altitude and find a good place they can grasp firmly. They then undergo the final molting of their exoskeletons of their lives.

A cicada partially exiting its old skin

     The skin (exoskeleton) splits along the back and slowly a white-colored, very soft-bodied adult cicada crawls out the back. Although the initial separation from the old nymph skin may only take a few minutes (though can take much longer too), the soft adult will cling, often by its abdomen, until its legs and rest of the body hardens and darkens enough to protect and carry its weight. This usually happens by the next morning. It then joins others of its kind, eventually forming massive choruses of males calling for females. Here's a video showing a cicada undergoing its final molt: 

A cicada starts to spread its wings and dry off as it is close to completing its final molt

     After mating, the females insert their rice-like eggs into twigs, preferring ones about the thickness of a pencil. If enough cicadas lay their eggs on a sapling, it can really hurt the young tree. On older trees it often just results in pruning of smaller branches. The small branches and leaves that die off, sometimes even breaking and hanging downwards, is referred to as "flagging." The eggs hatch and the young either fall to the ground or crawl out of the fallen branches until they find some tasty tree roots to feed on, feeding like this for the next 13-17 years. Both young and to a lesser extent adults feed by sucking plant juices, which is typical of this group of insects called Hemiptera. This cycle then repeats itself. 

The damage caused by the cicada inserting its eggs into a twig.

     That's what's supposed to happen and the vast majority of the time does happen. But there are exceptions. Sometimes periodical cicadas emerge either earlier or later, up to 4 years either way. These are referred to as stragglers. This has been recorded as happening since the early 1800's, so is nothing new. 
     The speeding up of development is called acceleration. It is often connected to weather and climatic changes. So for example, multiple hot and cold weather patterns may trick some into thinking it's passed multiple years and come out early. This is what may be happening locally now. Regardless why, we are having an early emergence in some local populations throughout the DC area. 
     So it may seem as though we have tons out now, but they're a very small percentage of the overall brood. Wait until we see the true appearance of Brood X in 2021! Sometimes when enough periodical cicadas emerge earlier (and plus or minus 4 years seems to be the most commonly occurring stragglers), it is believed that new broods may start. But it would take quite a few to emerge and then somehow survive so many years to start a new brood, at least in theory.
     No matter how many emerge, Periodical Cicadas are a favorite food of just about anything. You'll see birds gorging themselves on them, and this may well lead to many more nestling survivors in these times of plenty. Squirrels and other animals that normally don't regularly eat insects may now be seen stuffing themselves and their young with this fantastic food supply. I've even seen copperhead snakes feast on them.
     And animals aren't the only ones. In many cultures, including several Native American Indian tribes, people also feed on cicadas. In some cultures their names translate to "shrimp from land." They are low in fat, high in protein, and quite nutritious. Being arthropods like shellfish, those with that sort of food allergies may want to think twice, but it's not a big deal for others. Having said that, remember that they've been eating off the roots of trees for up to 17 years and so have absorbed in some cases what the trees have been exposed to. This could be mercury or pesticides, but in most cases, they are more than safe to eat. Indeed I always eat them when they emerge in huge numbers. While better fried with butter (and much more shellfish-like), you can also just eat them raw. They are best when they're soft-shelled, white and recently transformed. Otherwise you will have the extra crunch to contend with once they harden and darken as adults. Cicadas have a nutty taste to them. If you don't believe me, try them yourself. Or perhaps you can just be satisfied watch me eat one:

Eating a 17 Year Locust back in 2004

     So what we have now are stragglers from Brood X. I for one really look forward to this fantastic natural phenomenon which is rarely observed in the world, something that reminded people of the stories of insect plagues. For me though this is just a glimpse into the wonderful world of nature for which we have to wait so many years to witness again!

My son poses with a Periodic Locust from Brood II in the mountains back in 2013

Wednesday, May 10, 2017

Wild Rice Restoration

A small stand of Wild Rice.

     Wild Rice (Zizania spp.) has long been greatly valued as a food plant by both man and wildlife. Although now usually considered a gourmet delicacy, it once was a staple in the diets of Native American Indian peoples, indeed the most important food for some tribes. While there are three species native to North America, here in the DC area, Zizania aquatica is the Wild Rice we had growing naturally.
     Wild Rice is a tall annual plant in the Poaceae (Grass) Family. It grows in wetlands, usually in slow moving, fresh-brackish tidal waters. Growing in the water, it can still stand 10' tall. It was once a major component of some of our wetlands and rivers. It has since however disappeared from many of the places it was once common, including in Arlington County, Virginia. This is very unfortunate because of its value to both man and wildlife.
     The number of Native American Indian tribes making use of it is incredible. Locally, Captain Smith (of Pocahontas and the founding of Jamestown fame) made note of how common it was and its use by the Algonquian-speaking tribes he encountered, including the tribes making up the Powhatan. He stated that "this they use for dainty bread buttered with dear suet."
     But wildlife of course has been depending on Wild Rice for countless generations. It remains, where it is still found, one of the most important seasonal foods for waterfowl and many other wetland birds. It also provides excellent cover and nesting shelter for them, as well as a host of reptiles, amphibians, fish, mammals, and insects, including as a food plant for at least 5 species of caterpillar. So its disappearance from our local waterways was a major setback for wildlife.
     This is one reason that several local jurisdictions have made efforts to restore Wild Rice back to their wetlands, including Arlington. So last September of 2016, crews from various jurisdictions and environmental groups traveled to Jug Bay Wetlands in Maryland to collect seed to hopefully return this valuable plant to its historical range. Interestingly, Wild Rice had been at low numbers at Jug Bay as well, but had been successfully recovered. 
     Jug Bay's experience restoring it provided valuable lessons to the rest of us who wanted equally successful results in our own parks. Here's a short video documenting some of our rice collecting efforts. Please turn up the volume however, as the GoPro used in recording it was waterproof sealed and thus the sound is a bit muffled:    

Wild Rice, some bagged a week or so earlier so less ripened rice would fall into the water and not be able to be collected. Only a small percentage of the overall rice was bagged for collection, leaving always enough for regeneration and wildlife food. 

A seed head of ripe Wild Rice, bagged and ready to harvest. Note all the empty stems around it which have already released their ripe Wild Rice into the marsh.

Quite a few bags were collected, ready for cleaning, and shows you the great amount of food produced for wildlife, the results of its successful recovery at Jug Bay.

Wild Rice ready to be stored for cold stratification all winter.

     After the successful collecting trip, the Wild Rice was cleaned so just seed was preserved. This was stored in water in a refrigerator. This cold stratification process, while keeping it moist, is essential in getting it to germinate the following spring. The water is changed periodically during the winter storage (it's some really smelly water...) until later when it can be sowed. For Arlington, the original planting site along Four Mile Run where the stream restoration process in partnership with Alexandria was taking place, was not yet completed on the County side. This resulted in us making arrangements with our colleagues in the National Park Service to find suitable habitat that was within Arlington, but owned by the Service. This location, where Wild Rice historically grew, was Roaches Run.
     So after agreeing to help plant some on the Alexandria side together, staff from the City of Alexandria, Arlington County, and the National Park Service (with lots of advice from our friends at the Anacostia Watershed Society), all got together to help each other plant the Wild Rice at Roaches Run. This sort of inter agency partnership and sharing of resources happens all the time, allowing us to share knowledge, staff, and other resources to further all our conservation missions. What follows is a short account of how the Wild Rice was sowed, using mud balls and team work. Please disregard how windy it was that day:

A Wild Rice mud ball ready to be launched into the water at low tide. Note the rice seeds.

     Since this was our first attempt and this plant is an annual, this teamwork will have to be repeated until the rice takes hold. It is our hopes though that we can be successful in restoring huge Wild Rice stands along the tidal Potomac River in our area. This was just the first step in returning this species (and only one of many plants and animals we hope will also be recolonized) back to its historic haunts where it played such a vital role, but we all have to take first steps before we can run. In the future, we hope the natural landscape and all it supports will once again be there for future generations of people and wildlife to enjoy.

Wild Rice grains.

Friday, April 14, 2017

Arlington Bioblitz

Arlington's Bioblitz team from last year who assisted in the National Park Service Bioblitz

     Mark your calendars now. May 20th, 2017 is Arlington County's first Bioblitz, and you can participate and contribute. A bioblitz is a quick, but intense, biotic survey completed within a 24 hour period. Consider it a snap shot in time of what plants and wildlife are found in a certain place during that period of time. While this is certainly not a complete record of what lives there, it provides a vital look at what is there during that period. If you get enough snap shots, then you can get a clear picture of what's there. 
     The Arlington Bioblitz will kick off a much larger and longer survey of what we have in Arlington. Over at least a two year period, the results of this and even more surveys will help us know what we have, and compare it to what we have recorded before or what was historically present. This information will help shape the new update of the County's Natural Resource Management Plan. You can't manage and preserve what you don't know you have, so this info is vital. You can see the previous County Board approved plan here:  If you'd like to see the technical report (granted also in need of updating using new survey information) that resulted from our previous county biotic surveys, please check here:  
     The Arlington Bioblitz will kick off many more surveys where we will check on previous records and see how those plants and animals are doing (and get an idea of how our Natural Resources Management Plan has done). But we will hopefully also find new flora and fauna that can influence what the new Natural Resources Management Plan update will include. Some of this will be done by County staff, some by contracted experts, and much more with the aid of volunteers and citizen scientists.
     This is where the general public such as you comes in. We hope you can join us that day (and stick around to help with the surveys that follow) to record what you see. Join Bioblitz survey teams in various County parks. Perhaps you have an expertise and can help lead a team. Perhaps you can help be an extra pair of eyes or help record what is seen. We plan to use the iNaturalist application to collect most of the data. This where regular folks along with experts can record sightings, often using a photograph that can serve as a voucher of what was seen and which can be verified by others. More on this neat process here:
     So what is planned for Arlington Bioblitz May 20th? Our field base will be at Barcroft  Park, one of several parks that we have planned for surveying. These parks also include Glencarlyn, Long Branch, Gulf Branch, Tuckahoe, Fort CF Smith, Bluemont, even our colleagues at Potomac Overlook will be hosting teams. 
     We have some experts that will be leading some very interesting searches for mammals, reptiles, amphibians, fish, macroinvertebrates, birds, plants, and some insects such as bees. Most of the teams will be conducting their inventories from 10am-4pm, but a few such as the birders will get an early start. Want to help conduct some citizen science that day and join us? Start by checking here:   We also have a kickoff event, explaining a bit more about what and why we are doing this and other biotic surveys scheduled for the evening of April 18th. You can find out more about that event here: .
     Want to lead a team or get even more info? Contact Arlington County Parks Natural Resources Manager Alonso Abugattas at either or by phone at 703-2287742. Participating in a bioblitz is not only a lot of fun, but provides some valuable citizen science. Recording these nature discoveries helps us know what we have and how we can better protect them. But it is also a great hands-on way to learn from experts and one another, all in a social and and informative manner.

Friday, March 31, 2017

Spectacled Caiman

     I've been lucky enough to have had several encounters with Spectacled Caiman (Caiman crocodilus), the most recently on my trip to Central America. I've never seen so many as I have at Cano Negro near the Nicaraguan border. There were hundreds of them, specially emerging at night. Shining a flashlight on the water resulted in an incredible display of eyes glowing back at us. So I thought I'd tell you a little bit about them.

Caiman are nocturnal creatures

     Spectacled Caiman are the most abundant of all 25 of the crocodilian species. They're also called Brown, Common, or White Caiman, and have 3 subspecies. They range throughout both Central and South America. They've also been introduced (often as released or escaped pets) into Florida, Cuba, and Puerto Rico where they did not occur before.

     Spectacled Caiman do not get as large as other crocodilians. Males are larger and get to about 6.5 feet long. Females get to about 4.5 feet. They average 3-4 feet and 60 lb in general, but one was recorded at 8.2 feet and 128 lb. Their most common name comes from a distinctive bony ridge between the eyes which look like spectacles. Adults mostly have a grayish green coloration, but can get much darker during colder weather.

The bony ridge between the eyes give them their most common name: Spectacled Caiman

     Caiman have a varied diet, often depending on their own size and what's available. When small, they will eat insects, crustaceans, molluscs and other invertebrates. When they get larger, they prefer fish, but will eat waterfowl, mammals, and even each other. It's this generalized diet which has helped them to adapt to different habitats. They mostly feed at night. 

Spectacled Caiman are relatively non aggressive, even when surrounded by livestock.

     Though they may look intimidating, attacks on people are extremely rare, and when they occur, are almost always defensive in nature. In fact, they almost always flee when approached, as I know first hand. They do not even attack when you'd think they have a good reason to. I can give you 2 examples.
     On the first occasion, my wife Lucy and I were fording the Rio Frio on horseback. The water was about 3 or so feet deep when the horses were wading through, and we had to lift our legs to keep from getting too wet. Caiman, as usual, scattered as soon as we got close. At one point, Lucy's horse actually stepped on a medium sized caiman. The horse startled slightly and the caiman thrashed a bit as it swam away. Although it had every reason to bite, it never even tried to. 
    On another occasion, we were on a night excursion. We saw huge numbers of caiman every where. Our guide, one of the local cops, took us to an area used as a creche, a place where baby caiman all congregated for safety under the watchful eyes of female caiman. With our guide's permission, I caught a baby. I've handled crocodilians before and knew how to do so safely so as to not get bit. The little reptile though started squealing for help like they often do. Though this normally elicits a protective response, no mom showed up to defend it. Spectacled caiman really do try to avoid confrontation when they can.

A young caiman I caught protests loudly to my handling him.

     Female caiman are protective mothers however. Reaching sexual maturity in 4 - years, most caiman mate during the dry season. Females build nests during the wet season, mostly from vegetation, laying up to 40 eggs depending on the mother's size. The eggs hatch in 65-105 days, again heavily influenced by temperature. The decaying plant matter helps warm the eggs. Those eggs exposed to temperatures over 89 degrees Fahrenheit typically become females, lower than that and you get males.  
     The young are normally yellow in color with black spots. Babies congregate in certain areas in creches. Females take care of not only their own young, sometimes even carrying them on their backs, but of the others in the same area. Despite this excellent maternal care, predators such as tegu lizards, coati, and large water birds eat many of them.

     If they survive to adulthood, they are relatively safe from many predators. Though larger caiman, crocodiles, and jaguars take their share, man is their main threat. But because their skins have hard plates called osteoderms and their relatively small size, the market for their hides is much less pronounced than for other crocodilians. But the sides do yield some leather and hunting for food or out of fear does take place. Though their numbers are low in some countries such as El Salvador and Peru, in most others they are steady or growing. They are considered a species of least concern and in some places are legally harvested.

The American Crocodile riding low on the water is endangered world-wide, the Spectacled Caiman below it,with its protruding eyes, is the most common crocodilian. Crocs can get huge and will occasionally eat the smaller caiman.

     If nothing ends up happening to them, it is believed that they can live up to 75 years. Indeed, they have spread their range and are even considered invasive in such places as Florida and Cuba. The population in Florida really got established in 1992 after Hurricane Andrew allowed the escape of many captive specimens.
     But in their rightful environment, these are truly remarkable species, one that I always enjoy seeing in the wild. Here's a short video from the Capital Naturalist YouTube Channel showing them in Costa Rica:

How many Spectacled Caiman eyes can you count?

     For comparison, and much larger and rarer, here's a short video on my encoutnter with a Black Caiman while in a dugout canoe in Peru: