Many insects such as locusts, bugs, beetles, moths, butterflies and bees produce toxic or unpleasant substances that are either secreted by special glands or that are contained in the blood, stomach or other parts of theses insects’ bodies. Certain beetles are renowned for their ability to produce toxic substances. Two such groups of beetles, namely the net-winged beetles and leaf beetles are quite toxic and in the case of the flea-beetle, even potent.

Net-winged beetles or flat beetles (Lycus spp.) are all poisonous and therefore display aposematic colouration in combinations of orange and black patterns, which is mimicked by certain long-horn beetles and moths. The longitudinal ridges on the wings are characteristic of the net-winged beetles. They are slow flying insects that are very common on flower inflorescences and flower heads during the summer months. The larvae are predatory on other insects and look very similar to the larvae of the glow worms or fire flies. Eggs are laid under bark and in rotten wood, where the eggs will hatch and the larvae start feeding on other insects.

Leaf beetles are the fourth largest beetle family.

The most famous of these beetles are the arrow-poison beetles or flea beetles, the larvae of which are used by the san or Bushmen to poison their arrows. The most commonly used arrow poison is derived from the larva and pupae of beetles of the genus Diamphidia and Polyclada. Diamphidia is about 12 mm long, yellowish with small black dots. The antennae are unusually long for such a small insect. The young stages are yellow-brown and hairy with black heads. Older stages turn grey with black lines or series of black dots across the body. The head is black. There are no hairs on older larvae.

The larvae of Polyclada live on the leaves of Marula trees and those of Diamphidia on the leaves of commiphoras (Cork woods), especially the poison-grub commiphora (Commiphora africana).

The poison is applied to the arrow either by squeezing the contents of the larva directly onto the gut-binding between the shaft and the arrow head, by mixing it with plant saps to act as an adhesive, or by mixing a powder made from the dried larva with plant juices and applying that to the arrow tip. Interestingly the toxin, from these beetle larvae and pupae, called diamphotoxin, is non-toxic to mammals by ingestion and is only toxic after it enters the blood stream. Diamphotoxin is chemically unique, causing severe and extensive haemolysis, which is the destruction of the red blood cells with a subsequent release of hemoglobin the protein in the blood that carries oxygen from the lungs to the rest of the body

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Introduction

Adaptations for feeding are a conspicuous feature of avian evolution. These adaptations include modes of locomotion birds use while feeding, structure of the bill and the digestive system. Birds sit, walk, hop, fly and dive in search of food.

A bird’s bill is its key adaptation for feeding. The size, shape and strength of the bill affect a bird’s diet. Although seemingly specialised to one particular food or way of feeding, avian bills are multipurpose organs. Most birds feed on a variety of foods and may change diets with the season.
Three major features make up the general morphology of birds’ bills. The upper half of the bill, or maxilla, attaches to the brain case by a thin, flexible sheet of bone called the nasofrontal hinge. The lower jaw, or mandible, articulates with the quadrate (dentary bone), a large complex bone at the mandible’s posterior end. The large jaw muscles, which enable a bird to bite, attach to the posterior surfaces of the mandible.

Covering both jaws is a horny sheath of keratin, or ramphotheca, which may have sharp cutting edges, numerous tooth-like serrations or well-developed notches. The avian bill is not rigid as birds can flex or bend the upper half of the bill. It is furthermore equipped with many fine nerve endings that serve to feel and taste the food. In addition the bill is also used for protection, for display purposes and communication.

The oral cavity houses taste buds, pressure receptors and a tongue that is often specialised. The tongue aids in the gathering and swallowing of food. Most birds’ tongues have rear-directed papillae that aid in swallowing.

ADAPTATION IN BIRDS FEEDING ON ANIMAL FOOD

Fish

The following methods are applied in catching fish:

• Underwater pursuit and grasping or harpooning with the bill, e.g. penguins, darters and cormorants
• Diving or fishing from above the water’s surface and then caught with the bill or feet, e.g. wading birds, kingfishers and gannets
• Standing and waiting for a fish to appear and then stabbing it with the bill, e.g. wading birds
• Disturbing fish from the bottom with the feet and then stabbing or grabbing with the bill, e.g. wading birds
• Scooping fish with a gular pouch, e.g. pelicans

Meat

Meat is acquired by active predation or by scavenging. Active predators include the majority of birds of the order Falconiformis, most owls and members of the passerine families Laniidae (shrikes). Adaptation to a predatory lifestyle include the following:

• Large eyes with good binocular vision
• Large feet with long, sharp claws for killing and grasping prey
• A strong, hooked bill for tearing prey apart
• Excellent powers of flight

Only the vultures and the Marabou Stork have specialised in scavenging to the almost total exclusion of other foraging methods. The “griffon” vultures are characterised by the possession of a deeply troughed tongue with serrated edges and a stronger supporting tongue-bone than those of the other vultures.

Feeding on insects include foraging from surfaces such as the ground, branches or leaves, crevices behind bark or between flower parts and foraging in the air. Adaptations in plovers, for example, include long legs for running after insects and well developed nasal glands to remove salt from the body fluids of their insect prey, which enables them to be independent of drinking water.

Adaptations to aerial foraging include the small bill with very wide gape, the long wings and the streamline body, often ending in a forked tail.

The salivary secretions of woodpeckers are sticky, which helps them extract insects from wood crevices and ants from nests.

The Giant Kingfisher and Water Dikkop are crab specialists, both having large, strong bills. Sunbirds are basically the only group that feeds to a significant extend on spiders.

ADAPTATION IN BIRDS FEEDING ON PLANT FOOD

 Fruits

The most highly frugivorous of African birds are the louries, parrots, mousebirds, hornbills, barbets, orioles, bulbuls, starlings and white-eyes.

Frugivorous birds usually have robust bills for cutting through the tough skins of many kinds of fruits or for plucking them and swallowing them whole. Fruits favoured by frugivores are mostly black, red or orange in order of decreasing preference. Birds tend to avoid green fruits with few exceptions, e.g. the Yellowfronted Tinker Barbet that feeds on the green fruit of the mistletoe(Tapinanthus and Viscum).

Seeds

Seeds are processed in the following two ways among birds:

•  Birds that husk the seed and swallow the kernel only. These birds have conical-shaped bills that are mechanically strong.
• Their bills are also equipped with a cutting edge in both upper and lower jaws by which the husk of the seed is removed.
• Birds that swallow the seed and husk together and process both in the alimentary canal.

Nectar

Feeding adaptations among nectar-feeding birds include a tubular tongue for nectar extraction, a distensible oesophageal pouch (crop) for nectar storage and juxtaposition of the entrance to the digestive area (proventriculus) and the opening into the intestine. This anatomical arrangement allows nectar to bypass the stomach, while diverting insect food into the stomach for longer digestion. The gizzards of nectar-feeding birds are thin-walled structures. The tongues of sunbirds a brush-like tip with which nectar is licked up.

FILTER FEEDERS

Straining fine particles out of water has been evolved by at least three living groups of birds, namely the ducks, flamingos and prions. The adaptations to bill structure should be studied in each of these groups.

WOODPECKING

Tits, barbets and woodpeckers are among the most specialised birds that use woodpecking as a means of extracting food from wood. In these birds and especially the woodpeckers the following adaptations are noticeable:

• The rhamphotheca is especially hard and chisel-tipped and grows continuously.
• The broad base to the bill and hinge between the nasal and frontal bones of the skull.
• The broad base to the bill and hinge between the nasal and frontal bones of the skull;
• As well as the spongy bone between the skull and bill absorb the shock of striking the wood.
• The tail feathers are stiff-shafted to act as a prop against tree trunks.
• The zygodactyl toes allow for a better grip when negotiating vertical stems and branches
• The tongue has long hyoidal extensions that curl around and lie on top of the skull.
• This makes the tongue highly extensible, allowing it to probe deep into wood crevices

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We are all too familiar with that loud, incessant and sometimes deafening drone of the cicadas pulsing through the air during the warm summer months. As a matter of fact the sound is so persistent that people tend to ignore and sometimes become completely oblivious to it.

Here in South Africa some people refer to the culprits as Christmas beetles, which is a bit of a misnomer as they are not beetles but bugs belonging to the same group of insects as aphids, leafhoppers and spittlebugs. They are also around during most part of summer. In Australia the various species of cicadas have very descriptive and colourful names, for example Black Prince, Green Grocer and Double Drummer to mention but a few. Worldwide there are between two thousand and three thousand different species.

Most of a cicada’s lifecycle is spend underground where they live as nymphs feeding on the juices from tree roots by inserting their sucking mouthparts into the roots. Here they may spend years and go through several instars (developmental stages) and moults before finally emerging to go through a final moult outside on the trunk of a tree.

The carapace splits open lengthwise along the dorsal (top) side of the nymph to allow the new cicada into the outside world. It takes a while for the carapace and wings to harden before the cicada is ready for its adult life lasting but a few weeks. After mating, the female cuts slits into the bark of a twig and deposits her eggs there. When the eggs hatch after about six weeks, the newborn nymphs drop to the ground, where they burrow and start another cycle. Most cicadas go through a life cycle that lasts from two to five years, although some American species have a life cycle of seventeen years.

The intriguing question is how do these small insects produce that deafening sound and for what purpose? Well, the interesting thing about these noisy bugs is that only the males are calling. The reason? Well, to attract females of course. Each species has its own distinctive call and only attracts females of its own kind even though rather similar species may co-exist. The apparatus used by cicadas for producing the sound is quite complex and differ completely from insects such as crickets and grasshoppers in which sound is produced by means of stridulation, when different body parts are rubbed together.

The sex of a cicada is easily determined by looking at the underside of the insect. In females there is a pointed egg-laying organ (ovipositor) at the tip of the abdomen, which is absent in males. Instead, males have two semicircular plates, called opercula, which are situated at the base of the abdomen at its junction with the thorax and just behind the last pair of legs. The opercula cover the sound-producing and hearing organs. By lifting one of the opercula the tympanic membrane, used for hearing, can be seen as a whitish plate at the back of the cavity. The sound-producing organs, which are called tymbals, are situated at the side of the cavity behind the opercula. The hearing organs or tympanums are present in females but they lack the opercula and sound-producing organs.

The tymbals are ribbed membranes, each having strong muscles attached to it. Contracting and relaxing these internal tymbal muscles causes the tymbals to rapidly vibrate and produce pulses of sound. In some cicada species, a pulse of sound is produced as each rib buckles. The sound so produced is further amplified by the almost hollow abdomen and enlarged chambers derived from the tracheae (tubes conducting air to the internal tissues of an insect), which serves as a resonance chamber. The male can change the volume of the sound by lifting or lowering the opercula. This also gives the sound a ventriloquial quality making it difficult for human listeners to pinpoint the origin of the sound.

The most fascinating thing is that a certain group of African cicadas are among a very few insects that are capable of thermoregulating endothermically, in other words, they regulate their body temperature by means of their own internal cellular metabolism. Ectothermic organisms on the other hand, have to rely on external sources to regulate their body temperature. There are many advantages to endothermy, the most important being the ability of the males to control the quality of their calls as this is important to attract females. Endothermic males can much better regulate the temperature of their singing muscles, thus making their call characteristics much less variable and allow them to compete more effectively for mates.

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There are many misconceptions when it comes to the meaning of the terms game ranger, tour guide and nature guide and many people use these terms as if synonymous.  Although it could be confusing, there are however important and very definite differences in the application and meaning of these terms.

Game Ranger

A game ranger is a person whose concern is mainly with the conservation management of a specific area and usually does not deal with the general public in an educational role, although he or she could contribute towards a public general awareness of conservation. The prime responsibility of a game ranger is therefore to ensure the well being and safety of the protected area under his or her management. This is a multifaceted task which includes among other responsibilities the day to day monitoring of the health and well-being of wildlife, game capture and introductions, burning programs and local community relations, liaison and involvement.

Tour Guide

A tour guide takes people around a town, museum, or other tourist venue or specific areas of the entire country with a focus on cultural and historical aspects. It is a person who guides and interprets the cultural and natural heritage of an area, for which he or she possesses an area-specific qualification usually issued and/or recognised by the appropriate authority. Tourist Guides are able to help travellers understand the culture of the region visited and the way of life of its inhabitants. They have a particular role on the one hand to promote the cultural and natural heritage whilst on the other hand to help ensure its sustainability by making visitors aware of its importance and vulnerability.

Nature Guide

The nature guide forms a link between the natural environment and his or her guests with the emphasis on interpretation and education. He or she provides a learning experience which encompasses all aspects of wildlife and nature. Sharing factual knowledge and meaningful interpretation of the natural environment in an ethical way, is the main objective of nature guiding, which requires a high standard of training and quality service with the safety and enjoyment of people as priority.

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Most visitors to nature reserves where elephants occur are familiar with the deep rumbling sounds made by these giants of the bush. As a matter of fact, elephants have a considerable repertoire of sounds used in communicating over large distances. These sounds can vary from sub-sonic rumbles to very powerful screams and trumpeting reaching 112 decibels, almost as much as a jetliner taking off from 65 m away. Some of the intriguing questions that arise are how do elephants produce this wide array of sounds and how can they hear sounds inaudible to the human ear?

Just like humans, elephants produce vocal sounds when air expelled from the lungs is passed over the vocal cords of the larynx or voice box.

In elephants the larynx is about 8 cm long. The vocal cords vibrate when the air moves over them producing a particular sound. In elephants various frequencies of sound is produced by shortening or lengthening the vocal cords. Elephants also possess a resonating chamber consisting of the trunk, mouth, tongue, larynx, nasal cavities and pharyngeal pouch that enables the animal to modify and amplify the sound produced by the vocal cords. How the elephant holds its head, and flaps its ears presumably also affect the musculature around the larynx, which in turn modifies a call to achieve the desired sound.

mixture of higher frequency sounds can be produced depending on whether the elephant’s mouth is open or closed, whether the head is held high or low, the ears flapping slowly or rapidly, the position of the trunk and the speed and duration of air moving through the trunk.

Those low and deep rumbles that are often heard and referred to as stomach-rumbles are not the result of an upset stomach or knot in the digestive track, but very low frequency sounds that the elephants produce as part of their communication repertoire. Several physical-anatomical adaptations allow elephants to produce these low frequency rumbles.

First of all the large body of the elephant allows for a bigger resonating chamber and longer and looser vocal chords that contribute significantly to the production of these sounds. The bigger the resonating chamber and longer the vocal chords the deeper the sound.

The larger resonating chamber and longer vocal chords in elephants are attributed to the following features:

• The trunk in an adult male may add as much as three meters to the length of the resonating chamber.
• The loose arrangement of the musculature and cartilages that supports the tongue and larynx allows for greater movement and flexibility of the larynx.
• The loose arrangement of the tongue and larynx houses a structure unique to elephants called the pharyngeal (around the pharynx) pouch, situated at the base of the tongue, which further contributes to the production of low frequency calls.

The Pharyngeal Pouch

As mentioned before the pharyngeal pouch situated at the base of the tongue, is unique to elephants. Apart from the role it plays in producing low frequency sounds, it also provides elephants with an emergency source of water as elephants can store several liters of water in the pharyngeal pouch. On hot days or when tracking long distances over dry areas elephants are sometimes seen inserting their trunks down their throats and withdrawing water from their “stomachs”. In actual fact they withdraw water from the pharyngeal pouch. This water is then either drank or sprayed over the body as a cooling mechanism.

These low frequency rumbles of which the lowest components are below the lower limit of human hearing, travels further than higher frequency sound. It is therefore thought that the more powerful of these calls serve to communicate over long distances and thereby staying in touch with other elephants and family groups. The harmonic structure of these low frequency calls also allows elephants to determine the distance of the calling elephant.

At night an elephant is able to detect the call of another elephant almost 10 km away. During the day this distance drops dramatically to about 2 km because of the warmer surrounding air and wind.

Elephants are able to detect these low frequency sounds for several reasons. The large skull allows for longer ear canals, wider tympanic membranes and spacious middle ears. The amount of sound energy collected by the tympanic membrane (ear drum) increases with increasing membrane area, which in essence implies that the larger the tympanic membrane the better an animal is able to hear at low frequencies.

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