This paper is an essay about reproduction in wolves. It is divided in to three major parts. The first part deals with the thing of the topic which is the wolf. Here the various aspects of the wolves are discussed these are the species, social life, hunting, communication and lifecycle. The second part deals with the main idea of the topic which is reproduction in animals. In this part the reproduction in animals is discussed. The aspects of reproduction that are explained include; the male and female reproductive systems, mating, gestation period where fertilization is explained, parturition and birth are tackled. In the third part the thing and the idea of the topic are combined to answer the questions and hypothesis relating to reproduction in wolves. Here the various aspects relating to the reproduction of wolves are discussed. The parts examined are the male and female wolf reproductive system, mating and the gestation period of a female wolf in terms of fertilization, parturition and birth.
According to Whitt (2003) When the dog settled and embraced the community of human beings, its relatives continued to roam in the wild and they have become the most successful canid on the surface of the earth. According to Aamodt and Johnson (1987), the wolf is a wild dog and belongs to the group of animals that have the dog like traits. Scientists believe that they are direct ancestors of the present domestic dog. Even today the dogs and wolves have a lot in common. The average male wolf weighs between seventy and one hundred pound and measures from the nose to the tail, five to six point five feet (Aamodt &Johnson, 1987). The two also note that the female ones are smaller and weigh fifty five to ninety pounds and are between four point five and six feet in length (Aamodt &Johnson, 1987). Wolves have different colors with the majority having gray color shading but have the same body structure. Wolves like other canids have forty two teeth with twenty and twenty in the upper and lower jaw respectively. When they are moving or running, just like other canids, the wolves keep the back of their feet raised from the ground and this mode of movement is called digitigrades.
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Wolves are part of the canidae family which has over thirty five species including the foxes, coyotes, dingoes, jackals, dogs and the dholes. According to Mobile reference (2008), canids have long legs which are adapted for chasing their prey. All canids are digitigrades which means that they walk on four toes and their feet raised from the ground. They also have non-rectatile claws, bushy tails and dewclaws on their front feet. The canids also have a penis bone which is used for creating a copulatory tie during mating. The canids give birth to blind young one who opens their eyes after some weeks of being born. Most species in this family live and hunt as a group called pack. The wolves are classified in the canis genus since they are more doglike. According to Reiach et al (2002) there are three main types of species of wolves that is gray species which is the canis lupus, red species which is the canis rufus and the Ethiopian species which is referred to as the canis simensis wolves.
Wolf Anatomy and Taxonomy
According to Marshall Cavendish Corporation (2010) all animals are classified by the scientists in to taxonomic groups based on the anatomical, genetic and biochemical similarities and differences. Wolves like other animals fuel their body by feeding food from other organisms they have a dorsal chord called the notochord that runs their bodies. Marshall Cavendish Corporation (2010) also states that on the external taxonomy, the wolves are quadrupeds with a narrow body, bushy tail and deep chest. The wolves according to Marshall Cavendish Corporation (2010) have shaggy fur, large ears, and have a big head with a slender pointed snout. The same Corporation opines that the nervous system of the wolves is characterized by high intelligence, high vision and hearing capabilities and acute smelling sense. The wolves are lithe and athletic animals. They are also muscular around the neck, hips and shoulders. On their respiratory and circulatory system, the wolves are warm blooded with a typical mammalian circulation. They have large lungs and the larynx and vocal chords can produce a range of vocalizations. The wolves are committed carnivores with teeth that are suited for slicing the meat. They have a short and simple intestine and have a pair of kidneys used to remove metabolic waste through the blood.
According to Whitt (2003) the taxonomy of the wolf is as follows. It belongs to kingdom animalia which includes animals with multicellular organs that do not have the cell wall and cannot make their food, it belongs to phylum chordata which include the animals that do have backbones or internal support and fall under the class of mammalian which includes the animals with fur and can produce milk. The wolf order is carnivora which include animals that subsists chiefly on meat and is fall under canidae family which is a group of animals with dog like traits. It is of the genus canis. There are three species of the wolf namely lupus which is the grey wolf, rufus which is the red wolf, and simensi which is the Ethiopian wolf. According Whitt (2003) more than twenty four species have been identified but have in the recent times been reclassified into five sub-species, that is, the arctas which in this case is the name for arctic wolf, lycaon which is the eastern gray wolf, baileyi which is the Mexican wolf, nubilus which is the great plains wolf and finally occidentalis, which refers to the rocky mountain wolf. The sub-species can be distinguished from one another by use of size, fur color and the shape of the skull.
Figure 1: Wolf Taxonomy
Multicellular organisms that do not have cell walls and cannot make their own food
Animals that have backbone and internal support.
Chordates that have fur and produce milk
Mammals that subsist chiefly on meat
Carnivores that have dog like traits
Eastgern gray wolf
Source: Whitt (2003).
According to (Whitt, 2003), the gray wolves are the largest in canid family and the male can grow as much as six and half feet (two meters) and stand from twenty six to thirty inches high from the ground . The average weight for males ranges from seventy to one hundred and ten pounds with the weighing fifty to eighty pounds and reaching lengths of six feet. The gray wolf I s also referred to as tundra, timber or silver wolf (Whitt, 2003). According to Harrington (2002), of the three wolf species, gray wolves are the most common and are found around the northern hemisphere the other two are very rare. According to Harrington (2002), Gray wolves have adapted to different kinds of habitats. Have gray fur and are the largest members of the canid family. Adult wolves weigh from eighty to one twenty kilograms.
According to Animal Info (2005) Ethiopian wolves are diurnal. The wolves kill their prey and the kill is cached and retrieved later. They are both pre-eminent and cooperative hunters. Fuller (2004) observes the Ethiopian found is found in the in the Arabian peninsula, in northern Africa and in Ethiopian mountains. They live in pack of about two to twelve paired and related individuals. They prey on small and medium sized animals. They weigh about thirteen to eighteen kilograms. Harrington (2002) observes that the Ethiopian wolves are different from the gray and the red wolves. They are much smaller compared to the red and the gray wolves. They are only wolves that live in Africa. The scientist believed that the Ethiopian wolves were jackals. This is because they are they are smaller than the gray wolves, they are not stocky like the gray wolves instead they have long muzzles, long legs and slender noses just like the jackals and finally they eat small rodent which jackals love to eat.
The red wolves are found in North America, weigh between twenty and forty kilograms and live in pairs of between three and ten (Fuller, 2004). Red wolves are similar to gray wolves. Just like the gray wolves the red wolves live in packs and hunt the prey animal. They also care for their puppies and howl to protect their territory. However they are different from gray wolves in that they have more reddish fur and are smaller than gray wolves. Adults weigh only forty to ninety pounds.
Types Wolf Behavior
Wolf Communication Behavior
According to Wolf Haven International (2007) wolves use three types of communication namely the postural which involves the use of body language, vocal and olfactory which refers to use of smell. Olfactory communication involves scent marking which is mostly to mark boundaries, claim and defend the territories. Since they have scent gland in their toes they leave signature on all areas they go. They mark territories and food by urination. According to Wolf Haven International (2007) vocal communication among the wolves consists of howls, growls, barks and whines. They howl to claim territory or assemble the pack; whines are used by female as a sign of affection, growling is from the dominant wolves and are used to convey aggressiveness. Barking in wolves can be used to communicate excitement, raise alarm and call others to chase.
Socially wolves are organized in to packs. Aamodt and Johnson (1987), the wolves travel, hunt and perform most of their activities a group. The pack consists of members related by blood. They note that the core of the pack is a mated pair which consists of an adult female and a male. The other members are the offspring. They note that the packs may have six or seven wolves on average though the number may go up to fifteen. Like a family the members play different roles Aamodt and Johnson (1987.all the members of the pack are organized as a hierarchy with the breeding pair (alpha) at the top. At the middle of the hierarchy there are the subordinate called the beta and at the bottom there are wolves called the omega. The parent that is the alpha female and male is the oldest in the pack are involved in defending the territory and hunting due to their experience. They make important decisions like when to migrate or go for hunting. According to Aamodt and Johnson (1987) other pack members down the hierarchy are allocated roles that inferior to those of the members. The young puppies and the juvenile do not have an active role in the hierarchy and are not allocated any permanent positions. In the pack the time for dismissing some adult s from the packs depends on the availability of the prey and the number of wolves in the prey. The dispersed members may end up forming a new pack or may join other existing packs. According to Aamodt and Johnson (1987 the social structure of a wolf can be thought of as hierarchy consisting of the layers outlined below.
Figure 2: Wolf Social Structure
The alpha male and female
Beta male (this is the second ranking male sometimes mates with the alpha female)
Young subordinates both male and female(often dominated by the alpha young ones )
Male and female juveniles and pups
Male and female scapegoat(lives on the fringes of pack and may be mistreated by other members of the pack)
Source: Aamodt and Johnson (1987).
Reiach et al (2002) states that a wolf pack lives in a territory which must be characterized by enough fresh water and prey to feed the pack members. The territorial borders are marked with scent. They leave urine on scent post or upright marker for example tree stumps. The scents posts are constantly marked. Moves establish large territories in order to ensure that there is large supply of water and preys. The wolves mark their territories through methods such as howling, scent marking and direct attacks. Scent marking is done by ground scratching, defecation, and urination. In defending their territories wolves use scent marking which is done regularly and howling in order to prevent other wolves from entering the territories of other wolves. If these methods fail then the wolves may result into fighting the intruders and this can explain the high death rate of the wolves in the world.
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According to Defenders of Wildlife (2011), Wolves move, live and in packs consisting of four to seven animals. The pack consists of the mother, the father and the young one plus subordinate. The mother and father are referred to as the alphas lead the pack, track the prey, choose dens and mark the territory to be occupied by the pack.
According to Boitani (2003) the wolves after killing their prey, they start by feeding the parts that have the most essential nutrients. The alpha female and male who is dominant feed first. So the feeding order is determined by the roles played by the wolves in the pack Boitani (2003). Boitani also notes that the wolves do not feed on meat alone since they require a balanced intake of nutrients. The most important organ to the wolves is the live since it provides them with a variety of vitamins. They also consume the heart and the lungs due to their high palatability just like the liver (Boitani, 2003). They also feed on the bones which provide calcium and phosphorous to their bodies. When food is not enough the priority is given to the puppies.
According to Defenders of Wildlife (2011), wolves eat large hoofed animals such as the deer, elk and the moose and they also feed on animals that have died. On their part, Munoz et al (1994) opine that the wolves cooperate in hunting which enables them to bring down a prey. However wolves do not remain in the packs for long and this makes it difficult for them to know how to hunt as a group. Single wolves have a higher rate of succeeding in hunting than any other when they are working as a group. They find their prey’s through smell.
According to Boitani (2003) when wolves are hunting not all members are involved in the attack of the prey. The alpha wolves lead other wolves in chasing and attacking the prey. The pack may also be split in to smaller hunting groups although cooperative hunting is emphasized among the wolves. Wolves conceal themselves when approaching their prey. They may attack animals as a herd or may isolate an animal from the rest and then start chasing it. They try to catch the animal before it runs for a long distance but for the big animals the wolves chase them for long distances. One wolf may be involved in distracting the herd of the preys while others may attack the animals from behind. They may also use ambush where they chase their prey towards the areas they have set a trap such as areas where they have dug holes.
Denning and Sheltering Behavior
Wolves dig holes for their puppies and use areas with natural shelters for examples in areas with thick vegetation, cliffs found in river banks and cracks found in rocks. The dens are usually dug by the female wolves.
A wolf goes through series of changes. It is born, matures to an adult wolf which can mate or give birth (Reiach et al, 2002). The cycle begins with the birth pup. Pups are born in litters of two to seven wolves. They are fed by mother’s milk. When they are a month old they join a pack when they may stay for the rest of their lives or may leave to join other packs
Reproduction in Animals
According to Net industries (2011), during sexual reproduction in animals a haploid sperm and an egg cell combine forming a diploid zygote which divides mitotically into an embryo. After birth the young one grows into an adult that can reproduce. The animals bring the sperms and the eggs through internal or external ways. In animals sexual reproduction requires the joining of the male and the female egg. When they combine the result is formation of a zygote. Since the animals produce sexually the male and the female are involved. There animals with one reproductive cycle while there are those with more than reproductive cycle. The female undergo reproductive cycles while the male are always in reproductive activity. The female become receptive to male when they are undergoing ovulation. This state where the female is sexual receptive to male is referred to as estrus. Estrous cycle can therefore be used to mean reproductive cycle. In external fertilization aquatic environment is fundamental for the floating of the eggs before they are fertilized.
Male Reproductive System in Animals
In internal fertilization the male posses a copulatory organ called the penis which is used for transferring to the female the male eggs (sperms). According fails et al (2009) in animals the male copulation organ can be divided into three areas that is the glans or free extremity, body also called the main portion and two crura or the roots. The internal structure consists of erectile tissues called the corpora cavernosa and has the trabecaculae tissues. In fibrelastic penis the major part of the penis consist of the trabeculae tissues hence the penis remains erect even when not erect. In musculocarvenous penis the blood sinusoids dominate the penis. Erection in musculocavernous penis occurs when the blood flows to the penis and leads to increase in size and turgidity of the penis Reece (2009) while in fibroelastic penis such as that of the swine and the ruminants has no great enlargement as result of blood flowing. The male eggs are formed in mature males through process called spermatogenesis.
Female Reproductive System in Animals
According fails et al (2009) the female eggs are produced by the female reproductive tract. It deposits the eggs to an area where they can be fertilized by the male sperms. This placement provides a good environment for the development of the embryo and expelling the fetus. According fails et al (2009) the reproductive system consists of the vagina, vulva, two ovaries, two oviducts and the uterus. The ovaries are responsible for the production of eggs through ovulation. Through the oviducts the ova from the ovaries is conducted to the uterus. The vagina acts as the birth canal through which the fetus is delivered and acts as the sheath for the male penis during copulation. The vestibule is the area that is between the external genitilia and vagina. This area has a lot of mucous glands (Fails et al, 2009). The vulva is found on the external genitalia and consists of left and right labia which converge at the clitoris which consists of two roots that is the body and the glans. If fertilization occurs, the uterus provides a place for the development of the fetus Reece (2009). Through ovulation the female animals produce the female gametes. This happens periodically throughout the menstrual cycle.
During mating the penis is brought in to an appropriate position with the vulva of the female through a process called mounting (Reece 2009). According to him, successful mounting is preceded by a receptive stance by the female. In addition, he points out that that mounting can be affected if the male has a problem in the hind-limbs. The male animal introduces and maintains the penis in the vagina and this process is referred to as intromission this is enabled by the pelvic thrusts and abdominal muscles (Reece, 2009). The intromission time varies from one animal to the other. The stimulation continues and this leads to emission and ejaculation where the sperm oozes out of the penis into the vagina of the female animal. Sperm and fluids are ejaculated at the opening of the cervix in some animals while in others it occurs directly or partially in to the uterus.
Gestation period refers to the period conceived female carries, in the uterus, the embryo. According to Fail et al (2009) the interval extends from the fertilization of the ovum to the birth of the offspring. It includes fertilization early development the embryo in the lumen of the of the female reproductive tract implantation of the embryo in the uterine wall, the development of the fetal membranes and the continued growth of the fetus while in the uterus. Fail et al (2009) states that gestation period vary from species to species. Normal gestation is when the fetus is carried thought out the gestation period. If a premature birth occurs the fetus is born before it is fully developed and this is called abortion.
According Fail et al (2009) fertilization in animals occurs in the uterus. During copulation the sperms are deposited in to the female’s vagina. The condition where a female has a young one developing in the uterus is referred to as pregnancy (Fails et al, 2009). During pregnancy the animal experiences the development of the extra embryonic membrane which is used to feed the fetus and remove waste products. According Fail et al (2009) the placenta consists of chorion which is the outermost membrane, allantois which encloses the sac, and the amnion which is the innermost membrane.
Parturition and Birth
The end of pregnancy is marked by the parturition and involves giving birth. The act of giving birth is divided into three stages. The first stage involves the contraction of the uterine contracts to force the fetus to the cervix which takes a few hours. Secondly, the actual delivery takes place, from the cervix to the vagina. The third step involves the delivery of the placenta (Fail et al, 2009).
Wolves reach maturity at the age of two years. When the wolf have found a mate the courtship can last for many weeks. They are monogamous. When they mate the pair remains together in the pack. The age at which the wolves may start reproducing is influenced by the availability of food. The mating of the members of the same pack that is incest is not common among the wolves. According to Aamodt and Johnson (1987) it is only one pair of the wolves that is responsible for reproduction in a pack. It is only the alpha female and male who mate to produce offspring. Although there may be other pairs of wolves in the pack who can produce young ones, they do not in most cases mate. The alpha male uses dominance and force to discourage such wolves from forming pairs or mating. Breeding among the wolves is seasonal. This is because they experience one cycle of ovulation. All female and male wolves reach puberty at the age of twenty two months and they experience their first time production of the sperms and the ova.
The reproduction system in wolves has features that are not common with other mammals. The features of the reproduction is characterized by monogamy, monestrum with diestrous and proestrous phases that are prolonged, the lock and tie nature of their copulation, young adults being integrated into the pack and the leaders of the group suppressing the mating behavior of these young adults. Also wolves even the pseudo pregnant wolves that are those which do not get pregnant after matting are involved in the parental care of the puppies from the other wolves. Although the wolves experience one cycle of ovulation the chances of conceiving by the female are increased by the fact the both male and the female spend most of their time. For example when scent marking, the wolves do it together and this occurs when they are in proestrus phase. Also time in the estrus phase is lengthened thus the male and the female spend more time copulating.
Male Wolf Reproductive System
Males are twenty percent bigger compare to their female counterparts. They have a penis which supported by a bone called baculum the penis is tucked inside a skin called prepuce. In males that are mature sexually the testes are contained in a scrotal sac and hang between the hind legs. According to Marshall Cavendish Corporation (2010) male wolves have two sperm producing testes located in the external scrotal sac that hangs between the back legs. The Corporation also states that the sperms are produced in the area with the two testes. When the penis is inserted into the vagina of the female, the male wolf may ejaculate and the sperm pass along the urethra which runs through the penis.
The male reproductive system can therefore be seen as comprising of several parts paired testes, duct system, scrotum, the prostrate gland and the penis. The sperms are produced in the testicles and stored in the epidermis and they are transported through the vas deferens.
Female Wolf Reproductive System
Female wolves which are older than twenty two months are capable of giving birth to pups. The females are seasonally monoestrous which means they come into a condition of breeding once in every year. According to the US National Research Council, most of the female wolves in a pack, in one year, give birth to one litter. The committee also highlights that presence of many female wolves with producing potential in a pack makes others not to breed. According to Marshall Cavendish Corporation (2010) the female wolves have two egg producing ovaries and from each ovary a fallopian tube leads to the uterus which has two horns. Marshall Cavendish Corporation (2010) also states that the uterus expands greatly during pregnancy and can hold a maximum of eleven pups.
The female reproductive system of a female wolf can therefore be seen as consisting of various parts the ovaries which produce the eggs. After the eggs are produced, it travels through the oviducts to the uterus where it is supposed to meet the male egg and get fertilized. The uterus this is where the fertilized eggs stays and develops in to an embryo where the fetus results and finally into off spring of a wolf. In a female wolf there is a cervix found occupies uterus’ lower end and also occupies the upper part of the vagina. The vagina is the part of the reproductive system in the female wolf where the male wolf inserts the penis. Below the anus there is the vulva, this is the passage of urine.
Phases of the Reproduction
Boitani (2003) the reproductive behavior in wolves is related to the seasonal variation in the hormonal production. In autumn there is a rise testosterone hormone in males and estrogen hormones in males. The reproductive phases vary from individuals as a result of interplay of factor such as age, genotype, experience, latitude, body condition and the social environment.
According to Boitani (2003) this phase occurs early winter or late autumn before the female wolves can produce a discharge from the vagina. In this stage the both the male and the female may express unreciprocated interest in another mate. The flirtatious behavior of the female may be affected by change in hormones resulting form rise in level of the gonadotropin.
According to Boitani (2003), this begins when the bloody discharge and rapid growth in the uterine lining. The estrogen levels rise among the female wolves and the adult male s are usually attentive to the smell of the urine and the vulva. This is the communication means that are used for the newly formed pairs and who may be sexually naÃ¯ve. However males who have stayed with their mate may copulate (Boitani, 2003). According to Boitani (2003) the female wolves in this stage send signs to the male mates by prancing, body-rubbing, paw, nuzzling, placing their chin on the back of their males.
According to Boitani (2003), this is the stage in which there is copulation and the female is receptive. He further states that a receptive female wolf shows two behaviors that is flagging which means the female averts the tail to the side of the vulva or may stand still when the male wolf mounts. This phase can also be identified by a vulva that is swollen or soft. The male may respond to female’s stimuli by licking the genitals and the mounting on her. If a female is non-receptive it may pull away growl, roll over, shove the male wolf away or lie down. The male may spread their hind legs to enhance stability required during mounting. According to Boitani (2003) mounting is followed by pelvic thrusts while the forelegs of the male clasp the ribcage of the female. The thrusting continues until the male ejaculates and this is followed by expansion of the penile bulb (Boitani, 2003). The female wolves get stimulated by this expansion thereby contracting muscle of the uterus to squeeze the sperms to the ovaries.
According from Boitani (2003), Progesterone levels are high and pregnancy may result or not. Female wolves in this phase which do not get pregnant are referred to as pseudo pregnant. The males may abandon the pregnant female to look for other estrous females. Pregnancy can be identified by the loss of fur in the bellies and growth of the mammary cells. They may start constructing dens away from areas that can be attacked by other wolves
According to Marshall Cavendish Corporation (2010) the wolves’ courtship and breeding are inextricably bound up with their complex social life. Mating among the wolves is a fairly long- drawn-out affair. The penis of the male wolf swells when inside the female’s making it impossible for the male to withdraw. The two may remain locked for more than half an hour. This is to the advantage of the male since no other male that can mate with the female and this also enhances the chance of the male fertilizing the egg of the female (Marshall Cavendish Corporation, 2010).
According to Mech (2003) the gestation period for r wolves is about sixty- two to sixty- three. After the male wolf ejaculates the male egg travel and in less than a minute meet the female egg and as result fertilization occurs. The fertilization and the early stages of the development of the fetus occur in the in the oviduct and the embryo goes to the uterus after some days. After four weeks of pregnancy it is possible to observe enlargement of the abdomen. Still it is possible to observe mammary gland development as the hair starts to disappear. Parturition in female wolves is identified by decline in the progesterone level. When giving birth, the female wolf undergoes through three stages. Internally the wolf experiences contraction of the uterus relaxing the cervix. The second stage is the expulsion of the fetus from the uterus and finally is the period between the fetus expulsion and placenta expulsion marks the end of this final stage. Because they deliver multiple puppies they alternate between expulsion of the fetus and the placenta. During pregnancy the female wolf does not undergo any hormonal transformation and therefore it becomes hard to differentiate between a pregnant female wolf from a non-pregnant one.
According to Boitani (2003) the pups are born with their eyes closed. The number of puppies that a female wolf can have depends on the species of the wolf. For example the fray wolf can produce between four and six offspring although the number may go up to fourteen. In one litter the red wolf can give birth to between two and three pups. The arctic wolf on the other hand can give birth to between four and five pups. When they are born, all the members of the pack have the responsibility of raising the offspring. The health of the pups is determined by the food availability to the mother. The pups are accorded a lot of privileges and freedoms compared to other wolves that are ranked in the lower positions in the hierarchy of social structure.
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