Naraven pes?

Večkrat slišana/prebrana logika gre takole – pes spada med zveri (Carnivora) torej je karnivor (mesojed). V redu Carnivora najdemo zelo različne vrste, ki se med seboj močno razlikujejo tako morfološko, ekološko kot tudi vedenjsko. Naseljujejo praktično vse veg. cone, od tropskega pragozda do puščave, so samotarji, tvorijo krdela... Uživanje mesa ne velja za vse vrste v tem redu. Za domačo mačko rečemo da je obligatni karnivor, rdeči panda (Ailurus, fulgens) pa je specializiran za herbivorijo, pleni pa tudi majhne ptice in sesalce. Veliki panda (Ailuropoda melanoleuca) je specialist, hrani se z bambusom, vendar bo užival tudi meso, če je dostopno. (Thorne, 1995)

Družina psov (Canidae) je za razliko od mačk sposobna pridobiti vse pomembne nutriente iz rastlinskega materiala, v naravi pa njihovo prehrano predstavlja predvsem meso (Thorne, 1995). Kaj je volk je citirano spodaj, kaj pa psi? Ti preferirajo meso, kažejo pa tudi preference glede samih vrst mesa; govedina>svinjina>ovčetina>piščanec>konj. Poleg vrste mesa kažejo preference tudi glede priprave hrane oz. oblike v kateri je hrana. Tako imajo recimo konzervirano oz. pol-suho raje kot suho, kuhano meso raje kot surovo ter konzervirano raje kot kuhano (Thorne, 1995).

Coppinger in Coppinger (2001) trdita (v literaturi tej teoriji velikokrat rečejo kar Coppingerjeva), da so se psi udomačili sami (ti. self-domestication) zaradi nastanka nove niše-smetišč. Ko se je človek začel stalno naseljevati, so se okrog bivališč začeli nabirati odpadki. Tisti volkovi*, ki so bili manj plašni (»flight distance«), so bili v prednosti in počasi se je razvil pes. Ena od kritik je ta, da takrat, ko bi naj psi nastali, človek še ni živel v stalnih bivališčih, ampak se je selil, kar pa samo-udomačitve ne izključuje. Zelo poenostavljeno in zelo na hitro razloženo, bolj podrobno pa kdaj drugič ali pa v Coppinger in Coppinger: Dogs: A startling new understanding of canine origin, behaviour and evolution; Miklosi: Dog Behaviour, Evolution, and Cognition; Jensen: The Behavioural Biology of Dogs.).

Some 15,000 years ago, when humans traded a nomadic lifestyle for a sedentary one and the first villages were built, human-generated refuse began piling up around them: leftovers of family meals, butchering scraps, carcasses, by-products of farm animals, as well as human excrement. This newly created resource, the garbage dump, opened up a niche appealing especially to scavenger-prone carnivore species, with one caveat: tolerance to human proximity would have been the price to pay for admission. As Coppinger and Coppinger (2001) have suggested, dog domestication might indeed have taken this route: individuals who displayed lower flight distances towards humans around garbage dumps would have been seleceted to exploit this resource, and dogs' long-lasting co-existence with people would have thus begun. There is plenty of evidence today that village dogs gain food benefits by associating with humans. In fact, village dogs may depend entirely on human garbage for survival, as their hunting skills are not very effective. The reward for trading a hunting life for one of scraps may be that village dogs are rarely found in poor body condition. (Boitani s sod., 2007)

Do udomačitve naj bi prišlo v (južnem) delu vzhodne Azije pred približno 5400 – 16300 leti (Pal s sod., 2009), kar je veliko kasneje kot je predlagal Vila s sod. (1997). Poleg dokazov na podlagi genetskih analiz, na azijski izvor kažejo tudi morfološke podobnosti med kitajskimi volkovi Canis lupus chanco in psi (posebnost na spodnji čeljusti, ki je prisotna samo pri psih in kitajskih volkovih) (Pang s sod., 2009; Savolainen s sod. 2002). To posebnost imajo tudi indijski volkovi (Canis lupus pallipes (Koler-Matznick, 2002). Torej ni naključje, da je genetsko volku najbolj podobna pasma ravno shar pei? Je pa še ena možnost, za katero sumim, da bo ortodoksnim surovarjem daleč najmanj všeč. ;) For example, Olsen and Olsen (1977) noted that some wolves from China have a turned-back apex on the coronoid process of the ascending ramus (Chapter 4, Box 4.8, p. 91) similarly to extant dogs. They assumed that this similarity is based on homology and argued that dogs must have descended from those wolves. However, in passing they also mention that such a turned-back apex is characteristic for animals with an omnivorous diet (e.g. bears). Thus it is as likely that this feature evolves repeatedly in Canis species if they adopt an omnivorous diet (parallel evolution), making the character less feasible as a diagnostic signal for relatedness. (However, it seems not to be present in omnivorous jackals.) (Miklosi, 2007) Teorij vsekakor ne bo kmalu zmanjkalo. :)

Considering all this, we conclude that the mtDNA data in this study strongly indicate a single origin in time and space common to all domestic dogs, in southern East Asia approximately 5,400–16,300 ya (11,500–16,300 ya taking archaeological evidence into account), and that several hundred wolves were domesticated in this process. Alternative explanations for the dog origins cannot be excluded but demand far more complicated scenarios. (Pang s sod., 2009)

Morda zanimiv citat: In nature, wolves (in contrast to the omnivorous dogs) are practically strict carnivores (Thorne 1995), and feeding meat to a meat animal may seem an illogical expense. However, wolves are able to obtain all necessary nutrients from vegetable material (Thorne 1995) and Italian wolves, whose habitats have been severely encroached by human settlement, are estimated to obtain 60–70% of their food from garbage dumps, including a large proportion of vegetable substances, for example, spaghetti (Boitani 1982). (Pang s sod., 2009)

Če je torej udomačitev in nastanek psa posledica (zaradi človeka) nanovo nastale niše-nov vir hrane (iztrebki, ostanki uplenjenih živali, smeti,...), potem ne moremo reči, da je evolucijsko primerna prehrana psa enaka prehrani volka. Ker pes in volk naseljujeta različni ekološki niši in gre v bistvu za različni vrsti (ni mi všeč poimenovanje Canis lupus familiaris in me veseli, da kar nekaj avtorjev člankov, tudi recentnih, uporablja Canis familiars), ne moremo pri enem posnemati prehrane drugega. Pa tudi če bi jo... hej, v Italiji volkovi jedo špagete. Očitno jim še nihče ni povedal, da to ni naravno in da naj pri priči nehajo.

Če se nam zdi res mus nekaj oz. nekoga posnemat, zakaj torej ne posnemati prehrane prostoživečih psov? Ti so »našim« definitivno bližje kot pa volkovi... Ti. vaški psi (village dogs) se prehranjuje predvsem z odpadki, smetmi, na smetiščih, poleg tega smeti iščejo tudi med človeškimi bivališči. Večina je samotarjev, občasno se opazi tudi pare ali trie, večje skupine pa so redke, razen v primeru zbiranja okrog vira hrane oziroma samcev okrog godnih samic. Ok, ampak oni niso »naravni«, ker se še vedno potikajo okrog človeških bivališč, kar pač ni naravno. Torej je potrebno najti tiste, ki so »kao« res naravni...divje pse, prostoživeče pse s. str. (feral dogs).

Podatki so prav zanimi. Kot plenilci so ti psi neprimerno manj učinkoviti kot njihovi divji sorodniki (=volkovi), dokazov o napadih na živino je presenetljivo malo (namesto divjih, živino napadajo potepuški psi), lovijo sicer divjad (predvsem manjše živali, našli pa so tudi ostanke divjega prašiča in srne), primarni vir hrane pa lahko predstavljajo predvsem človeški odpadki in živalski kadavri. Prav tako prostoživeči psi lovijo (ogrožene) morske legvane, kapibare, ježevce, želve, opažen je bil celo uspešen napad na kojota...

On the basis of all reviewed studies it seems reasonable to conclude that feral dogs show a generally low predatory attitude, a low kill rate (efficiency of predation), have potential limits in prey size and are indirectly dependent on humans for food. Notwithstanding the inherent weakness of their predatory behaviour, feral dogs can be a serious nuisance to local farmers and a threat to protected wildlife despite efforts to control their numbers, especially in protected areas. (Boitani s sod. 2007)

Ja, in kaj zdaj, ko vsi žrejo take ali drugačne odpadke? Nič, ker svojih psov ne hranim naravno (torej z mrhovino, odpadki in sem ter tja kakšnim crknjenim malim sesalcem), ampak tako kot jim ustreza.

Koga zdaj posnemati oziroma ali sploh koga posnemati? Kaj ni bolje gledati lastnega psa in prehrano prirediti njemu, njegovim potrebam, ne pa neki romantični obskurni ideji o volkovih.

(To še ni končna verzija, se nadaljuje in popravlja ob priliki.)
*-ne bi šla v detajle glede skupnih prednikov ipd., ker bo samo težje razumet.
Viri:

Boitani L. 1982. Wolf management in intensively used areas of Italy. V: Parrington FH, Paquet PC, editors. Wolves of the world. Park Ridge (NJ): Noyes Publications. p. 158–172.

Boitani L., Ciucci P., Orlotani A. 2007. Behaviour and social ecology of free ranging dogs. V: The behavioural biology of dogs. Serpell J. (ed.).

Pang, Kluetsch C., Zou X., Zhang A., Luo L., Angleby H., Ardalan A., Ekstrom C., Skollermo A., Lundeberg J., Matsumura S., Leitner T., Zhang Y., Savolainen P. 2009. mtDNA Data Indicate a Single Origin for Dogs South of Yangtze River, Less Than 16,300 Years Ago, from Numerous Wolves.

Savolainen P., Zhang Y-P., Luo J., Lundeberg J., Leitner T. 2002. Genetic evidence for an East Asian origin of dogs. Science. 298:1610–1613.

Thorne C. 1995. Feeding behaviour of domestic dogs and the role of experience. In: Serpell J, editor. The domestic dog, its evolution, behaviour and interactions with people. Cambridge: Cambridge University Press. p. 103–114.

Vila C., Savolainen P., Maldonado J.E., Amorim I.R, Rice J.E., Honeycutt R.L., Crandall K.A., Lundeberg J., Wayne R.K. 1997. Multiple and ancient origins of the domestic dog. Science. 276:1687–1689.

Nekaj citatov za vse tiste s fiksno idejo, da imajo doma volka in da ga morajo temu primerno tudi hraniti. (vse Peterson in Ciucci, 2003)

While the wolf is popularly viewed as a consumate carnivore, it belongs to a family of carnivores that is adapted to feeding on a diverse array of foods. Wolves and other canids obtain most of their food from prey, but they are not exclusive meat eaters, or hypercarnivores, like the many species of cats. Throughout their evolutionary history, wolves have been shaped as cursorial predators of large herbivores, their characteristic niche. Yet, as generalist carnivores, wolves can effectively hunt prey that range in size, from 1 kg snowshoe hares to 1000 kg bison, and they can even subsist on garbage. (p. 104)

The adaptability of the grey wolf is best exemplified by its highly variable diet throughout the world. The economy of a wolf in Canada's Yukon is likely to be based on moose, while a wolf living in certain areas of Mediterranean regions may subsist largely on garbage and domestic animals. (p. 106)

In part of Eurasia, wolves live in areas with relatively little wild prey, but subsist nevertheless on a wide variety of foods provided indirectly by humans. Foraging garbage dumps, wolves eat meat scraps and various fruits, as well as inadvertently consuming nonfood debris... Perhaps because of the greater availability of fruit, wolves in southern portions of Eurasia may feed on plant material more extensively than those in North America. ...Fruit may provide vitamins for wolves in summer, as even in North America it is not uncommon to find seeds from raspberries and blueberries in wolf scats. Cherries, berries, apples, pears, figs, plums, grapes, melon, and watermelon have been reported in wolf scats. Grass merits brief mention, as it appears in wolf scats in North America as well as in Eurasia with 14-43% frequency. (p. 109)

Because the diet of dogs is also a domestic product, we should draw parallels carefully between the wolf and its domestic derivative. Nevertheless, the basic anatomy and physiology of digestion is probably conservative – we might expect that the dog lacks some enzyme systems or physiological capacity that wolves retain, but it is unlikely that dogs would exhibit physiological innnovations or capacities not shared with wolves. (p. 115)

The pancreas, under hormonal control, secretes more digestive enzymes, including proteases (for proteins), lipases (for fats) and amylase (for carbohydrates) ,... (p. 116)

Easily digestible items pass through the digestive tract more slowly than do foods with indigestibile components. When the proportion of raw fiber in the diet of dogs was experimentally increased from near zero to 8%, passage time was reduced from 60 – 70 hours to 35 hours. (p. 125)

Vir: Peterson R. O., Ciucci P. 2003. The wolf as a carnivore. V: Wolves: Behaviour, Ecology, and Conservation. Mech D., Boitani L. (ed.). 2003.