Defense (biology)
Defense in the biological sense refers to all strategies in animals and plants by which damage from predators or parasites , in the broader sense also from environmental influences, is to be prevented or at least reduced. Defense mechanisms in interactions between predators and prey can be divided into primary and secondary defense mechanisms.
Predator-prey interaction
The interactions often include five levels:
- Perception and recognition of the prey by the predator and their prevention through primary defense mechanisms by the prey
- Approaching the prey
- Escape of the prey and pursuit by the predator (a secondary defense)
- Resistance and (secondary) defense against prey
- Overpowering and consuming the prey
Active defense mechanisms of a prey animal are also called anti-predator behavior .
Primary Defense Mechanisms
Avoidance strategies and passive protective measures are used in a variety of ways. They work before an enemy attacks.
camouflage
Many animals hide or adapt to the environment in order not to attract the attention of predators : by shyness, long flight distance , camouflage ( walking leaf , stick insect , chameleons ) and by sound absorption by means of hair (moths wear against the ultrasound location of the Bats a hairiness). Many animals are nocturnal, they hide during the day. Plankton sinks in daylight so that it is less noticeable.
Buildings serve as hiding places, but can also act as external security, especially if they make access difficult or have emergency exits. Thus, beaver habitats not regulated with water height above the input of about 60 cm open to predators except otters. Other underground burrows have several escape routes (fox, meerkat).
Another form of camouflage is mimesis , the imitation of inedible natural objects (immobile, inanimate objects).
Warning color
Poisonous animals often signal their toxicity with warning colors .
Mimicry works accordingly , i. H. feigning a larger or poisonous species.
Secondary Defense Mechanisms
Locomotion
They act as a reaction to an encounter with a predator, usually as an active defense. Like humans, animals react to threatening situations with fear. However, defense actions cannot be strictly generalized, because they occur species-specific (SSDR, English species-specific defense reaction ( s ) ). Three behavioral patterns are possible: firstly, a careful assessment of the situation, secondly, confrontation, flight, retreat or hiding, and thirdly, panic, often “headless” escape or “blind” attack.
There are three active strategy options when the flight distance is exceeded: flee, hide motionless or defend.
Escape
In contrast to plants and fungi, many animals have the opportunity to flee ( escape behavior , stampede ), some hit hooks ( hare ), crawl into holes (mice) or burrows (rabbits, marmots) on trees. Birds , flying insects , flying squirrel , Gleitbeutlern escape into the air, moths can be covered with ultrasound locating, climbing animals can sink (spherical beetles ).
Squids can hide behind clouds of pigment or luminous clouds in the deep sea.
To support the escape, sometimes the repelling or expelling of body parts ( sea cucumber ), sacrificial body parts that can still twitch and grow back later (e.g. lizards , predetermined breaking points in grasses), some organisms escape the hunt.
Hide
Escape behavior often results in looking for a hiding place and remaining motionless there. Some burrowing animals or aquatic animals on the ground have developed strategies to escape by digging into the ground.
Defensive battle
In direct confrontation, defensive animals can initially express threatening behavior through noises, gestures, stamping on the ground and thus demonstrate their defensiveness. Alternatively or in parallel, substances that serve as signals to keep people away can be emitted ( allomones ).
As a result, they can go into a defensive battle . In the event of an attack (example: a mother defends its offspring) or preventively, for example in the case of birds to defend a breeding colony. Bites, also with poison , beak blows, stings, poison stings, stings ( porcupines ), blows, e.g. As with hooves or reinforced body parts (spur of the cock, spiny-tailed), education fist of man, collisions with horns , antlers , defenders and trunk ( mammoths ), tail (ponytail against flies), defense by body mass (large relative small) Release of stinging hair , spitting of saliva ( lama ), defense secretions or poison ( spitting cobra ), spraying of hot, poisonous liquid ( bombardier beetle ) or smelly secretions ( skunk ).
Bites with and without fangs , stitches with a sting ( platypus ) or by other active measures ( deer ) often serve both the defense against enemies captured and to overwhelm animals or be used for intraspecific disputes.
Other defense reactions consist in hygiene , detergents against pathogens and in the immune defense against bacteria , parasites and viruses based on their exogenous biopolymers .
Mechanical defense
Outer shell
An outer shell in particular represents passive protection. This applies to both plants and animals. This includes more or less solid eggshells . Even single-celled organisms such as foraminifera are able to wrap tightly, fungi form spores capsules . Solid bark protects against predators and, for a short time, against heat and fire. Nutshells or solid seed pods are appropriate protective devices. Many mollusks use solid mussel shells or snail shells . The skull of vertebrates and humans protects the central nervous system, the embedding in the vertebral canal also serves to protect the spinal cord . The best passive protection is full body armor. The majority of all animals, the articulated animals , have an exoskeleton made of sclerotin with embedded chitin fiber molecules. Bone armor of turtles , armor of stegosaurs , placodermi , pangolins , armadillos and the Indian rhinoceros , placoid scales of cartilaginous fish , elasmoid scales of bony fish , horn scales of snakes and lizards have a similar effect .
However, the armor reduces mobility.
Some animals also puff themselves up and enlarge their body volume in order not to be devoured ( puffer fish , porcupine fish ), others bristle their coat for this purpose.
Reinforcements
Another possibility is the formation of armored body parts in exposed places, for example needles , spines or thorns ( hedgehogs , roses, agaves , sloe , robinia , blackberries , many tendrils and grasses, crown-of-thorn starfish , cactus plants ). Hard, smooth or hairy leaves and reinforced leaf edges protect against snail damage and other predators such as larvae or smaller vertebrates. Heavy hair and thick skin protects against bites and stings.
Additional protection is provided by mechanisms that release toxins on contact, e.g. B. nettles or fire jellyfish , which are specially designed to provoke a strong pain provocation.
Another strategy, which cannot protect the individual, but builds on the learning experience of the predator, is to prove to be inedible through embedded needles ( sclerite of glass sponges ), and lignin storage by wood plants.
Optical defense
Optical active defense mechanisms can scare costume deflection behavior or shock Rigid include.
A special form of optical defense when fleeing consists in the fact that the attacked animal draws the attention of the predator to itself in the course of its flight and lures it away from the unprotected but still undiscovered clutch.
Many animals adopt the strategy of initially becoming immobile when threatened (mouse). Some maintain this strategy even in major threat situations (cicadas, chameleons, sloths ), some can pretend to be dead ( opossum ) or remain rigid in uncovered terrain ( mane jumpers ).
Acoustic defense
An active acoustic defense can consist of stridulation .
Chemical defense
A strategy that cannot protect the individual but builds on the learning experience of the predator is to prove to be inedible through inedible or poisonous body parts or superficial secretions. Among the poisonous plants, for example, milk- sap-containing milkweed plants and alkaloid-containing plants are known. Among the animals there are especially poison-sequestering poison dart frogs , butterfly larvae and nudibranchs .
Some wood plants have tree resins to ward off injuries. Other plants react by releasing chemically active substances.
Social strategies
In addition, social animal communities have developed further strategies for active defense, for fleeing or for hiding in the crowd (primary defense): social body care against parasites, swarming behavior ( schooling fish , birds), collective attention (crickets, waterfowl), common defensive battles.
Sea turtles and other marine animals hatch synchronously so that more young animals survive.
For plants see also
literature
- Jessica Hullinger: 7 Absolutely Insane Animal Defense Mechanisms In: mental_floss, October 6, 2013, accessed July 10, 2015.
Individual evidence
- ↑ a b c d e f g Konrad Dettner: Poisons and pharmaceuticals from insects - their origin, effect and ecological significance. (PDF) In: Entomologie heute 19, 2007, pp. 3–28.
- ↑ NABU: Amphibian and Reptile Protection Current
- ↑ DPJ Kuijper, E. Sahlén, B. Elmhagen et al .: Paws without claws? Ecological effects of large carnivores in anthropogenic landscapes Section 3 b
- ↑ a b On the hunt with radar ( Memento from April 3, 2011 in the Internet Archive ) On the hunt with radar: Seeing with your ears. Defense mechanisms of moths against bats
- ↑ a b Rosana Shuhama, Cristina M. Del-Ben, Sônia R. Loureiro, Frederico G. Graeff: Animal defense strategies and anxiety disorders. In: To. Acad. Bras. Ciênc. , Volume 79, No. 1, 2007, doi : 10.1590 / S0001-37652007000100012 .
- ↑ a b c Michael S. Fanselow: Neural organization of the defensive behavior system responsible for fear. In: Psychonomic Bulletin & Review , Volume 1, No. 4, 1994, pp. 429-438, doi : 10.3758 / BF03210947 .
- ↑ a b Robert C. Bolles: Species-specific defense reactions and avoidance learning. In: Psychological Review. Volume 77, No. 1, 1970, pp. 32-48.
- ↑ Michael S. Fanselow: Species-specific defense reactions: Retrospect and prospect. In: Mark E. Bouton, Michael S. Fanselow (Eds.): Learning, motivation, and cognition: The functional behaviorism of Robert C. Bolles. Pp. 321-341, Washington, DC, 1997, American Psychological Association ( abstract ).
- ↑ Michael H. Morgan, David R. Carrier: Protective buttressing of the human fist and the evolution of hominin hands. (PDF) In: Journal of Experimental Biology , Volume 216, 2013, pp. 236–244, DOI (incorrectly stated): 10.1242 / jeb.075713.
- ^ T. Ryan Gregory: Another just-so story, this time about fists. In: Genomicron , December 21, 2012, viewed July 9, 2015.