North American box turtles breathe continuously during locomotion, and the ventilation cycle is not coordinated with the limb movements Landberg et al. El basilisco es representado en algunas culturas como una gran serpiente con una mancha en la cabeza con forma de corona que con la mirada, si es directa, es capaz de matar y, si es indirecta, petrifica. The big advantage of plant derived enzymes is that they can be pre-digesting food in the stomach for 60 minutes or much longer before the digested food even gets to the small intestine where it can be absorbed. August 21, at 7: They may become embedded in the prey and may even be swallowed with the prey. If this temperature requirement is not met the food will simply rot in their gut and not be digested, resulting in elevated uric acid levels, and an acidic blood pH level causing detrimental damage to your reptile. However, there are certain exceptions such as the absence of external ears in snakes they have the inner and middle ears.
The energy requirements for their poikilotherm metabolism are very low which allows large animals from this class such as various constrictors and crocodiles to survive for months from one large meal, digesting it slowly. Herbivorous reptiles are also unable to masticate their food, which slows down the digestive process. Some species are known to swallow pebbles and rocks that help in grinding up plant matters within the stomach, assisting their digestion.
The basic nervous system in the Reptiles is similar to that in the Amphibians. But, Reptiles have slightly larger cerebrum and cerebellum. Most of the important sensory organs are properly developed in these creatures. However, there are certain exceptions such as the absence of external ears in snakes they have the inner and middle ears. Reptiles have twelve cranial nerve pairs. They have to use electrical tuning for expanding the range of their audible frequencies because they have short cochlea.
These animals are believed to be less intelligent compared to mammals and birds because the relative size of their brain and body is much smaller than that of the latter. However, the brain development can be more complex in some larger Reptiles. Modern species also have pineal glands in their brains. Most of these animals are tetrapods, meaning they have four legs. Snakes are examples of legless Reptiles.
Their skeletal system is similar to other tetrapods with a spinal column supporting their bodies. Their excretory system consists of two small kidneys. The diapsid species excrete uric acid as the principal nitrogenous waste product. But, turtles excrete mainly urea. Some of these species use their colons for reabsorbing water, while some are able to absorb the water stored in their bladders. Certain Reptiles excrete the excess salts in their bodies through the lingual and nasal salt glands.
Reptiles have certain characteristic features that help in distinguishing them from Amphibians, Mammals and Aves:. They are capable of adapting to almost all kinds of habitats and environmental conditions, except for extremely cold regions.
These animals can inhabit dry deserts, forests, grasslands, wet meadows, shrub lands and even marine habitats. Reptiles are capable of adapting to extremely high temperatures because they are cold blooded. Various snakes including the Rattle Snakes and King Snakes as well as different lizards like the Gila Monsters live in desert habitats.
Grassland is another common type of habitat for various snakes and lizards e. Garter Snakes, Fox Snakes. The vegetation in this habitat attracts many insects and rodents, making it easier for the Reptiles to catch prey. Swamps and large water bodies are inhabited by different Reptiles such as crocodiles, alligators, certain turtles and snakes. Animals like the Saltwater Crocodile and Marine Iguana inhabit seaside, travelling in and out of ocean as necessary. Some species, such as the Sea Snakes and Sea Turtles, live in the ocean.
They leave the waters only during the breeding season for laying eggs. These animals typically practice sexual reproduction with some specific species using asexual reproduction.
Majority of these animals are amniotes, laying eggs covered with calcareous or leathery shells. The eggs are generally laid in underground burrows dug by the females.
The viviparity and ovoviviparity modes of reproduction are used by many species such as all boas and many vipers. However, the level of viviparity may vary with some species retaining their eggs until shortly before hatching while others nourish the eggs for supplementing the yolks.
In some Reptile species, the eggs do not have any yolk with the adults providing all the necessary nourishment through a structure resembling the mammalian placenta. Six lizard families and one snake family from the Squamata sub-group are known to be capable of agamogenesis or asexual reproduction.
In some squamate species, the females are capable of giving birth to unisexual diploid clones of themselves.
This type of asexual reproduction is known as parthenogenesis, occurring in various teiid lizards, geckos and lacertid lizards. Komodo dragons have reproduced through parthenogeny in captivitiy. Like many mammals, birds and Amphibians, their embryonic life consists of an amnion, chorion, as well as an allantois.
The incubation period may vary depending on the species and other factors like the temperature of the surroundings. Usually, hatchlings are able to take care of themselves almost immediately after coming out of the eggs. But, the females of some species are known to protect their eggs and hatchlings. For example, female Pythons coil themselves around the eggs in order to protect them and regulate their temperature.
Similarly, crocodiles are known to guard their young after the eggs hatch. TDSD or temperature-dependent sex determination can be observed in many Reptiles.
In TDSD, the incubation temperature determines the sex of the offspring. This characteristic is most commonly seen in crocodiles and turtles, but can also occur in tuataras and lizards. Different food habits can be observed between the four sub-groups.
Animals belonging to the Crocodilia, Squamata and Sphenodontia sub-groups are carnivores, feeding on a wide range of prey from vertebrates to fish and insects. The Testudines are herbivorous in nature with their diet comprising of fruits, shrubs, leaves, grass and marine plant materials like kelp and algae. The populations of many Reptilian species are facing rapid decline due to various factors like deforestation, loss of habitat, hunting for hide and to use them for edible purposes.
Various Reptile populations have faced extinction in some specific locations. Due to these reasons, many species are protected by law in most of the countries where they are found. Many Reptile species, including various lizards and turtles, are very popular all over the world as exotic pets. There is a widespread popularity even for the venomous snakes, especially among keen animal lovers.
However, there is a common misconception that these animals do not need as much care as required by mammal pets. The truth is that, Reptiles need to be taken care of properly; otherwise, they cannot survive in captivity. They should be kept in large tanks or cages where they can move freely. Such venom is dangerous only if it gets into an open wound. Always wear protective clothing when handling rattlesnakes. Female rattlesnakes are ovoviviparous.
That is, they produce eggs that are retained, grow, and hatch internally. The young of most species of rattlesnakes are 6 to 8 inches 15 to 20 cm when born. They are born with a single rattle or button, fangs, and venom. They can strike within minutes, but being so small, they are not very dangerous. Average broods consist of 5 to 12 young, but sometimes twice as many may be produced.
The breeding season lasts about 2 months in the spring when the snakes emerge from hibernation. Sperm is thought to survive in the female as long as a year. During summer, pregnant females usually do not feed, so few are ever captured that contain eggs about to hatch.
The young are born in the fall. Most rattlesnakes are mature in 3 years, but may require more time in northerly areas. Rattlesnakes may not produce young every year. The sex of a rattlesnake is not easy to determine.
Even though the tail of the rattlesnake the distance between the vent and the rattles is quite short, it is much longer in males than in females of the same size.
The paired hemipenises of male snakes are not visible except during mating, when one of these paired hollow organs is turned inside out and extruded from the cloaca. If both are extruded artificially, they appear like two forked, stumpy legs. Snakes never close their eyes, since they have no eyelids. They are deaf, but can detect vibrations. They have a good sense of smell and vision, and their forked tongues transport microscopic particles from the environment to sensory cells in pits at the roof of the mouth.
A rattlesnake uses these pits to track prey it has struck and to gather information about its environment. Snakes have a large number of ribs and vertebrae with ball-and-socket joints. The snake accomplishes its smooth flowing glide by hooking the ground with its scales, which are then given a backward push from the ribs.
Rattlesnakes often look much larger when seen live than after they have been killed. This happens because their right lung extends almost the full length of the tubular body, and when the snakes inhale they can appear much fatter and more threatening. The expulsion of the air can produce a hiss. Rattlesnakes, like other snakes, periodically shed their skin.
When the new skin underneath is formed, the snake rubs its snout against a stone, twig, or rough surface until a hole is worn through. After it works its head free, the snake contracts its muscles rhythmically, pushing, pulling, and rubbing, until it can crawl out of the old skin, which peels off like an inverted stocking.
Each molt produces a new rattle. Some rattles usually break off from older snakes. Even if no rattles have been lost, they do not indicate exact age because several rattles may be produced in one season. Even though the optimum temperature for rattlesnakes is around 77 o to 89 o F 25 o to 32 o C , the greatest period of activity is spring, when they come out of hibernation and are seeking food.
If lizards are active, be alert for rattlesnakes. The activity period for rattlers can vary from about 10 months or so in warm southern regions to perhaps less than 5 months in the north and at high elevations. Depending upon availability of good, dry denning sites below the frost line, rattlesnakes may hibernate alone or in small numbers. If not, the snakes might emerge too early in spring only to become sluggish and vulnerable should the weather again turn cold.
Since snakes are cold-blooded animals and their body temperature is altered by air temperature, refrigeration makes them sluggish and easy to handle for displaying.
Rattlesnakes usually see humans before humans see them, or they detect soil vibrations made by walking. They coil for protection, but they can strike only from a third to a half of their body length.
Rattlers rely on surprise to strike prey. Once a prey has been struck, but not killed, it is unlikely that it will be struck again. Experienced rodents and dogs can evade rattlesnake strikes. Rattlesnakes may appear quite aggressive if exposed to warm sunshine. Since they have no effective cooling mechanism, they may die from heat stroke if kept in the sun on a hot day much longer than 15 or 20 minutes. If a rattlesnake has just been killed by cutting off its head, it can still bare its fangs and bite.
The heat sensory pits will still be functioning, and the warmth of a hand will activate the striking reflex. The head cannot strike, but it can bite and inflict venom. The reflex no longer exists after a few minutes, or as long as an hour or more if it is cool, as rigor mortis sets in. The greatest danger to humans from rattlesnakes is that small children may be struck while rolling and tumbling in the grass. Only about 1, people are bitten and less than a dozen people die from rattlesnake venom each year in the United States.
Nevertheless, it is a most unpleasant experience to be struck. When known to be abundant, rattlesnakes detract from the enjoyment of outdoor activities. The human fear of rattlesnakes is much greater than the hazard, however, and many harmless snakes inadvertently get killed as a result.
Death from a rattlesnake bite is rare and the chance of being bitten in the field is extremely small. Experienced livestock operators and farmers usually can identify rattlesnake bites on people or on livestock without much difficulty, even if they did not witness the strike.
A rattlesnake bite results in almost immediate swelling, darkening of tissue to a dark blue-black color, a tingling sensation, and nausea. Bites will also reveal two fang marks in addition to other teeth marks all snakes have teeth; only pit vipers have fangs too.
Rattlesnakes often bite livestock on the nose or head as the animals attempt to investigate them. Sheep, in particular, may crowd together in shaded areas near water during midday.
As a consequence, they also frequently are bitten on the legs or lower body when pushed close to snakes. Fang marks and tissue discoloration that follows in the major blood vessels from the bite area are usually apparent on livestock that are bitten see Wade and Bowns , pages 32 and 34 in the Damage Identification section of this book.
Most species of rattlesnakes are not considered threatened or endangered. Since they are potentially dangerous, there has not been much support for protecting them except in national parks and preserves.
However, since there are state and local restrictions, contact local wildlife agencies for more information. An occasional single poisonous snake can be destroyed if one has enough determination. In areas where the habitat is favorable for rattlesnakes, copperheads, or water moccasins, a significant reduction in their population density may be difficult. The fencing must be tight. This process is referred to as 're-energizing the boundary layer.
Unpredictable predators -- The use of space by predators in relation to their prey is a poorly understood aspect of predator-prey interactions. Classic theory suggests that predators should focus their efforts on areas of abundant prey, that is, prey hotspots, whereas game-theoretical models of predator and prey movement suggest that the distribution of predators should match that of their prey's resources. If, however, prey are spatially anchored to one location and these prey have particularly strong antipredator responses that make them difficult to capture with frequent attacks, then predators may be forced to adopt alternative movement strategies to hunt behaviorally responsive prey.
Roth and Lima examined the movement patterns of bird-eating Sharp-shinned Hawks Accipiter striatus in an attempt to shed light on hotspot use by predators. Their results suggest that these hawks do not focus on prey hotspots such as bird feeders but instead maintain much spatial and temporal unpredictability in their movements.
Hawks seldom revisited the same area, and the few frequently used areas were revisited in a manner consistent with unpredictable returns, giving prey little additional information about risk. But why wouldn't Sharp-shinned Hawks focus their hunting on the areas with the most potential prey bird feeders?
One possibility is that behaviorally responsive prey diminish the "hotspot" quality of feeders. Although feeder hotspots are sources of abundant prey, the individuals at such feeders generally benefit from group vigilance as a result of these higher densities. As a result, the vulnerability of the prey may actually be lower at feeders than at other locations.
In addition, unpredictable movement may reflect a sort of "prey management" by predators, whereby predators spread their hunting activity over multiple areas in an effort to avoid inflating the antipredator behavior of their prey. This hunting strategy may be effective when prey are anchored to high-resource areas such as feeders and use antipredator behaviors, such as high vigilance, that reduce a predator's attack success if it attacks frequently and predictably.
Seabirds are choking on ocean plastic video. The tongues of cormorants and other fish-eating species are small because these species swallow prey whole and tongues are not needed to manipulate or position food in the oral cavity.
Dorsal view of the surface of the lower bill of a Great Cormorant Phalacrocorax carbo. Arrow shows the tongue with sharpened tip. Scale bar, 12 mm. Lateral view of the cormorant tongue. The tongue and the small anterior and posterior areas of the mucosa of the bill are covered by white keratinized epithelium. Black arrow shows short base of the tongue.
White arrow shows the median crest on the dorsal surface of the tongue. A, anterior; B, posterior. Scale bar, 3 mm Source: Detailed view of the horny tip left of the Guadeloupe Woodpecker tongue in vivo position Villard and Cuisin Dorsal view of the tongue of the Spotted Nutcracker Nucifraga caryocatactes.
Arrows show two elongated processes of the apex. A, apex, B, body, R, root, LP, laryngeal prominence. Scale bar, 3 mm. Lateral view of the tongue of the nutcracker. Arrow shows elongated processes, pointed diagonally, B, body, R, root. Hummingbird tongues are fluid traps, not capillary tubes -- Hummingbird tongues pick up a liquid, calorie-dense food that cannot be grasped, a physical challenge that has long inspired the study of nectar-transport mechanics.
Existing biophysical models predict optimal hummingbird foraging on the basis of equations that assume that fluid rises through the tongue in the same way as through capillary tubes. Rico-Guevara and Rubega found that hummingbird tongues do not function like a pair of tiny, static tubes drawing up floral nectar via capillary action.
Instead, the tongue tip is a dynamic liquid-trapping device that dynamically traps nectar by rapidly changing their shape during feeding. In addition, the tongue—fluid interactions are identical in both living and dead birds, demonstrating that this mechanism is a function of the tongue structure itself, and therefore highly efficient because no energy expenditure by the bird is required to drive the opening and closing of the trap.
These results rule out previous conclusions from capillarity-based models of nectar feeding and highlight the necessity of developing a new biophysical model for nectar intake in hummingbirds. Hummingbird tongue tips twist to trap nectar.
How the hummingbird tongue really works with videos. Close encounters with possible prey. You want to live 10—20 years. You are peering under leaves, poking into rolled ones, searching around stems, exploring bark crevices and other insect hiding places. Abruptly an eye appears, 1—5 cm from your bill. The eye or a portion of it is half seen, obstructed, shadowed, partly out of focus, more or less round, multicolored, and perhaps moving. Now, a safe few meters away, are you going to go back to see whether that was food?
Associated body patterns often suggest other head and facial features, which in turn enhance the eye-like nature of the spots. None of these patterns exactly matches the eyes or face of any particular species of predator; but, even when quickly and partially glimpsed, all give the illusion of an eye or face. These false eyes are mimicking the eyes and faces of such predators of insect-eating birds as snakes, lizards, other birds, and small mammals, as perceived at close range by the insectivorous birds in their natural world.
Note the distended throat of this American Kestrel. Pigeons generally lay two eggs one day apart, which hatch 18 days after they are laid. A similar substance is produced by flamingos and male Emperor Penguins.
The normal function of the crop is food storage. Pigeon 'milk' also contains IgA antibodies and antioxidants carotenoids. The avian stomach is divided into 2 parts:. Photomicrograph 50X of a cross section through the proventriculus showing folds of mucous membrane P ; deep proventricular glands GP ; capsule connective tissue around the glands arrow head ; muscle layer m ; serosa connective tissue with blood vessels S , and the lumen L From: Photomicrograph X of longitudinal section of the gizzard showing folds of mucous membrane lined by simple prismatic epithelium P ; simple tubular glands Gs in the lamina propria constituted by connective tissue Lp ; secretion of glands S that are continuous with the cuticle or koilin ; C , part of muscle layer m , interpersed with bundles of connective tissue Tc From: Photomicrograph X of the koilin of an Eclectus Parrot Eclectus roratus.
Note the regular, columnated structure of the koilin layer K and its association with the glandular epithelium E of the ventriculus From: De Voe et al. A, koilin, B, crypts, C, glands that secrete koilin, D, epithelial surface, E, desquamated epithelial cells, 2 Mucosa of the gizzard. A, koilin, B, secretion in gland lumens and crypts, and 3 Koilin layer. A, secretion column, B, koilin-layer surface, C, horizontal stripe indicating a 'pause' in secretion of the koilin, D, cellular debris.
Eglitis and Knouff Vultures of the seas -- Animals are primarily limited by their capacity to acquire food, yet digestive performance also conditions energy acquisition, and ultimately fitness. Optimal foraging theory predicts that organisms feeding on patchy resources should maximize their food loads within each patch, and should digest these loads quickly to minimize travelling costs between food patches. GPS-tracking of 40 Wandering Albatrosses from the Crozet archipelago during the incubation phase confirmed foraging movements of between — km, giving the birds access to a variety of prey, including fishery wastes.
Using miniaturized, autonomous data recorders placed in the stomach of three birds, the first-ever measurements of gastric pH and temperature in procellariformes were obtained. Such low stomach pH gives Wandering Albatrosses a strategic advantage because it allows a rapid chemical breakdown of ingested food and rapid digestion.
This is useful for feeding on patchy, natural prey, but also on fishery wastes, which might be an important additional food resource for Wandering Albatrosses. It is likely that this physiological characteristic evolved as a response to a diet largely composed of squid, and to a patchy distribution of this food resource resulting in large, infrequent meals.
The strategy of Wandering Albatrosses is to cover long distances rapidly and at low costs to increase the probability of encountering dispersed prey patches whose distribution is unpredictable. Knots with large gizzards consumed far more molluscs with shells than the birds with smaller gizzards. Birds with smaller gizzards simply couldn't feed fast enough. By allowing them to crush more shell per gizzard-full, larger gizzards gave birds the edge.
Thus, even though it is energetically costly for the knots to maintain a larger gizzard, when the bird needs to get the most out of its crunchy diet, it's a price worth paying. So, the birds' gizzards enlarge as they fatten for migration. Because the molluscs' shells stay the same size as the molluscs shrink, the amount of shell a bird must process to eat its fill also increases.
But with their larger gizzards, the birds can still make the most of even the crunchiest winter diet! Within 14 days, they showed a doubling of the size of their gizzards. Red Knots have strong muscular gizzards for feeding on molluscs. A shift back to a mussel diet induced about a doubling in gizzard mass in just a few days.
As the knots were fed progessively smaller mussels day 22 to day 46 that are easier to crush, gizzard mass again declined. A switch back to a soft food pellet diet caused a further decline in gizzard mass. Finally, a switch back to a mussel diet again cause a rapid increase in gizzard mass From: Piersma and Drent Ostrich Struthio camelus stomach. Note how particle size of material in the gizzard ventriculus is smaller than in the proventriculus due to the grinding action of the muscular walls plus small pebbles gastroliths.
The capacity to reduce particle size is related to the metabolic demands of a species. Therefore, particle size reduction is often considered the key digestive difference between ecto- and endotherms that allows endotherms to rely on shorter digesta retention times without losing digestive efficiency, and hence facilitate the high level of food intake necessary to meet their increased metabolic requirements.
In contrast, adaptations for chewing intrinsically increase the weight of the head. The use of the gizzard system has the potential advantages that intake rate is not limited by chewing, that no investment in dental tissue is necessary, and that dental wear is not a determinant of senescence as observed in mammals.
The absence of age-dependent tooth wear might even be a contributing factor to the slower onset of senescence in birds as compared to mammals.
On the other hand, the use of a gizzard requires the intake of suitable grit or stones—an action that represents, in the few studies where this has actually been quantified in birds, a relevant proportion of feeding time Fritz et al.
Gastrointestinal tracts of a carnivorous hawk, an omnivorous chicken, and 4 herbivorous birds. Note larger size of crop in omnivore and herbivores, and particularly in hoatzin. Ceca are small in hawks and relatively large in grouse. Although ceca are relatively small in Hoatzins , Emus, and Ostriches, an expanded foregut Hoatzins , a much longer midgut Emus , or a much longer colon Ostriches compensates for this From: Stevens and Hume Over-reliance on the passive pathway provides metabolic advantages and ecological constraints.
It does provide birds with an absorptive process that can deal with rapid and large changes in intestinal sugar concentrations. The passive pathway is also energetically inexpensive to maintain and modulate. However, passive absorption through the paracellular pathway is dependent on concentration gradients. In the absence of a transport system that selects which materials to absorb, this non-discriminatory pathway may also increase vulnerability to toxins, and thus constrain foraging behavior and limit the breadth of the dietary niche of the birds.
Another problem is that when luminal sugar concentrations are lower than those in plasma, glucose may diffuse back into the lumen. Cross-section of the intestine ileum of a Spotted Tinamou Nothura maculosa.
Villi are lined with columnar epithelium EP , including goblet cells arrows that secrete mucus. The muscle layer includes longitudinal fibers MI on the perimeter, circular fibers Mc , and additional longitudinal fibers at the base of the villi muscularis muscosae; MM From: Chikilian and de Speroni Blue-headed Parrots at clay lick.
Meyer-Rochow and Gal determined that the pressures involved could be approximated if they knew the 1 distance the feces traveled, 2 density and viscosity of the material, and 3 shape, aperture, and height of the anus above ground. How penguins choose the direction of defecation, and how wind direction factors into that decision, remain unknown.
Avian Pancreas tissue Source: The Avian Digestive Tract. Avian geophagy and soil characteristics in southeastern Peru. Luminal morphology of the avian lower intestine: Histological aspects of the stomach proventriculus and gizzard of the Red-capped Cardinal Paroaria gularis gularis.
Comparative study of the digestive system of three species of tinamou. Crypturellus tataupa, Nothoprocta cinerascens , and Nothura maculosa Aves: Journal of Morphology Journal of Experimental Zoology Rictal bristle function in Willow Flycatcher. Dysplastic koilin causing proventricular obstruction in an Eclectus Parrot Eclectus roratus. Journal of Avian Medicine and Surgery Anatomy and physiology of the digestive system in fowl.
Pages in Proc. An histological and histochemical analysis of the inner lining and glandular epithelium of the chicken gizzard. American Journal of Anatomy An ecomorphological study of the raptorial digital tendon locking mechanism. Dietary and developmental regulation of intestinal sugar transport. Digesta retention patterns in geese Anser anser and turkeys Meleagris gallopavo and deduced function of avian caeca. Comparative Biochemistry and Physiology A Histological and global gene expression analysis of the 'lactating' pigeon crop.
Vultures of the seas: Evolution of the structure and function of the vertebrate tongue. Journal of Anatomy Light and scanning electron microscopic study of the tongue in the cormorant Phalacrocorax carbo Phalacrocoracidae, Aves.