Evolution

• Learning Outcomes


  • Understand the evolutionary history of dogs and the last remaining lineage Caninae
  • Recognise important physiological aspects such as the wide morphological range within a species
  • Understand the traits (physical and behavioural) that have been altered during domestication
• Carnivorans


  Evolved from miacoids about 55 Mya during the late Palaeocene
• Carnivorans split


  50 Mya, into two main divisions: caniforms (dog-like) and feliforms (cat-like)
• The first clearly identifiable member of the dog family Canidae had evolved


  40 Mya

  
• Canidae family subdivided


  • Hesperocyoninae (~39.74-15 Mya)
  • Borophaginae (~36-2 Mya)
  • Caninae lineage that led to present-day canids
• Each of these Canidae groups showed an increase in body mass with time, & sometimes exhibited a specialised hyper-carnivorous diet that made them prone to extinction
• Only the Caninae lineage, commonly referred to as "canines", survived to the present day
• Canid-like species over time

  • Fennec fox
  • Arctic fox
  • Cape hunting dog
  • Dhole
  • Maned wolf

  
• Genus Canis (True Dogs)

  • Black-backed jackal
  • Coyote
  • Gray wolf
  • Golden jackal
• Species of Canis often hybridise in the wild
• The critically endangered Red Wolf (Canis rufus) is thought to be a stabilised hybrid between Grey Wolf & Coyote
• Wolf breeds


  Exhibiting one-person fidelity
• Jackal breeds


  More promiscuous in their affections
• Subspecies of Grey Wolves

  • Arctic wolf
  • Indian wolf
  • Arabian wolf
  • European wolf
• Juliet Clutton-Brock's model: dog breeds primarily from Indian wolf, but with input from local subspecies
• Early dog domestication


  14,200 years BP
• Early dog domestication


  • Bonn-Oberkassel dog
  • Ein Mallaha in the upper Jordan valley (Israel)
• The phylogeny of the 34 canid species shows that grey wolf & dog are most closely related, followed by a close affiliation with coyote, golden jackal & Ethiopian wolf, three species that can hybridise with dogs in the wild
• Wolf pack structure


  • Dominant pair patrol boundaries, settle disputes, control pack movements, do all the breeding
  • Hierarchy maintained by movements of tail, ears, mouth & body, & by vocalisations
  • Subdominant females more aggressive than males
• Wolf pack size


  • Northern wolf packs gather in groups up to 30 in winter to hunt large prey such as moose; in spring & summer, these break up into smaller basic packs (4-10) to hunt small prey (& to breed)
  • Southern wolves remain in basic packs
• Wolf territoriality


  • Scent marks placed along paths on conspicuous landmarks
  • Borders marked very intensively
  • Other pack members often "endorse" scent marks by dominant members
  • Howling marks territory, & is a cohesion mechanism within the pack
  • Territory size 60-400km2 (up to 12,800 km2 in one Alaskan study)
• Wolf hunting


  • Northern wolves: hunting is a very social activity, preceded by bonding ceremonies (tail-wagging, whining, mutual face-licking)
  • Kill efficiency is low: for moose, 8%; for smaller deer 25-63% according to snow conditions
  • Young prey more vulnerable in spring & summer, older animals in autumn & winter
  • Sex ratio of kills, males: females - 2½:1
  • Southern wolves kill gazelles, sheep, goats & hares; commonly hunt singly
• Wolf helper system


  • Subordinate members of pack are offspring of previous years; may delay dispersal till second or third year of life
  • A helper may take part in the hunt, or stay with pups while other pack members are away
  • On returning from a hunt, all pack members – helpers as well as dominant pair – regurgitate meat for the pups
• Wolf breeding


  • At breeding time, much chorus howling, muzzling, fur sniffing, increase in play and increase in aggression, which may result in change of ranking
  • Real fights are silent, loser runs away, often chased by all pack members
• 2013 Nature Paper identified 10 genes with key roles in starch digestion & fat metabolism that appeared to be selected for during the domestication of dogs, indicating that novel adaptations allowing the early ancestors of modern dogs to thrive on a diet rich in starch, relative to the carnivorous diet of wolves, constituted a crucial step in the early domestication of dogs
• Evolution of Working Dogs

  • Dogs may have originated as scavengers, domesticated for use as food & fibre or put to work, but also make excellent companions
  • To understand the evolution of working dog behaviour, you need to look at ways a wild animal (such as a wolf) could be transformed into a "tameable" & trainable companion
  • Sled dogs, Livestock Guarding dogs, Herding dogs
• Sled Dogs


  • Modern racing sled dogs are a good example of how working dogs are selected & how a breed is created
  • Early races were recreational tests of hard-working, freight pulling dogs & drivers transporting people, goods & mail
  • Winning teams lope at speeds of 32kph
  • Racing dogs must be morphologically efficient, minimising mass & maximising speed
  • Existing population of fur trapper's or Inuit dogs supplemented by large numbers of dogs arriving as part of the Alaskan Gold Rush (1896)
  • By 1908 – 1st All-Alaskan Sweepstakes race, breed differences were still apparent but uniformity of size & conformation was shown by the best teams
  • Sled dogs acquired & bred according to gait, good sled dogs lope or gallop with no flight (i.e. one foot is always in contact with the ground)
  • Speed is a combination of both rapidity of movement & length of gait, length of gait determined by the dog's size & shape
  • Matched gaits (as important as speed) – minimises energy lost to vector forces
  • Physics of sled pulling: single dog pulls 100%, 2-dog team 85%, 6-dog team 50%, more than 12 dogs adds no net gain
  • Dogs selected & trained for different positions on the team

  
• Uniformity of size & conformation


  • Shown by the best sled dog teams

  
• Sled dogs


  • Resembling the modern-day Alaskan husky

  
• Sled dogs


  Acquired & bred according to gait

  
• Good sled dogs


  • Lope or gallop with no flight (i.e. one foot is always in contact with the ground)

  
• Dogs that have flights (floaters)

  Ineffective sled pullers
• Speed of sled dogs

  • Combination of both rapidity of movement & length of gait
• Length of gait


  Determined by the dog's size & shape (larger the dog, the longer the gait)
• Factors affecting length of gait

  • Slope of pelvis, distance between shoulder blades & length of back
• Matched gaits


  As important as speed, minimises energy lost to vector forces
• Physics of sled pulling

  1. Single dog pulls 100% of the load

  2. Each dog in a 2-dog team pulls 85%

  3. Each dog on 6-dog team pulls 50%

  4. More than 12 dogs - adds no net gain
• Sled dog positions


  • Immediately in front of the sled - two wheel dogs
  • Fastest pair of dogs at the front of the team
  • Shouldn't be significant difference in performance between the fastest & slowest dog
  • Super-fast lead dogs try to tow the team
  • Dogs that show agonistic behaviour are disruptive & not used

  
• Fighting in sled dogs

  Can be minimised by pairing males with females
• Selection against sexual dimorphism to preserve uniformity of gait in sled dogs