How can we achieve more accurate reporting of average dog lifespan?

Despite major advances in our understanding of dogs as a biological system (including genetics/epigenetics, physiology, cognition, and behavior), the veterinary field lacks consensus around a critical piece of information: namely, the average lifespan/life expectancy of a domestic dog. This deficiency is due in part to unavailable and/or inconsistent collection of dog mortality data. In an effort to review historical and current reports of dog lifespan to determine whether the domestic dog's lifespan has changed over time, we found that incongruous data were prohibitive to conducting a formal meta-analysis of dog lifespan reports. However, in examining several different kinds of dog aging and mortality studies covering a span of about 40 years (1981 to 2023), it seems apparent that the median lifespan of domesticated dogs has not recently decreased, as has been reported in the popular press, but rather has increased steadily over that time frame. Still, assessing the validity of these numbers is a challenge, as methodology, cohort, and covariates (such as weight, breed, etc) vary from study to study. We therefore recommend the adoption of a comprehensive, standardized method for reporting and recording dog mortality so that a more accurate understanding of dogs' average lifespan can be obtained in the future.

Raising an Eye at Facial Muscle Morphology in Canids.

The evolution of facial muscles in dogs has been linked to human preferential selection of dogs whose faces appear to communicate information and emotion. Dogs who convey, especially with their eyes, a sense of perceived helplessness can elicit a caregiving response from humans. However, the facial muscles used to generate such expressions may not be uniquely present in all dogs, but rather specifically cultivated among various taxa and individuals. In a preliminary, qualitative gross anatomical evaluation of 10 canid specimens of various species, we find that the presence of two facial muscles previously implicated in human-directed canine communication, the levator anguli occuli medialis (LAOM) and the retractor anguli occuli lateralis (RAOL), was not unique to domesticated dogs (Canis familiaris). Our results suggest that these aspects of facial musculature do not necessarily reflect selection via human domestication and breeding. In addition to quantitatively evaluating more and other members of the Canidae family, future directions should include analyses of the impact of superficial facial features on canine communication and interspecies communication between dogs and humans.

What Is Written on a Dog's Face? Evaluating the Impact of Facial Phenotypes on Communication between Humans and Canines.

Facial phenotypes are significant in communication with conspecifics among social primates. Less is understood about the impact of such markers in heterospecific encounters. Through behavioral and physical phenotype analyses of domesticated dogs living in human households, this study aims to evaluate the potential impact of superficial facial markings on dogs' production of human-directed facial expressions. That is, this study explores how facial markings, such as eyebrows, patches, and widow's peaks, are related to expressivity toward humans. We used the Dog Facial Action Coding System (DogFACS) as an objective measure of expressivity, and we developed an original schematic for a standardized coding of facial patterns and coloration on a sample of more than 100 male and female dogs (N = 103), aged from 6 months to 12 years, representing eight breed groups. The present study found a statistically significant, though weak, correlation between expression rate and facial complexity, with dogs with plainer faces tending to be more expressive (r = -0.326, p ≤ 0.001). Interestingly, for adult dogs, human companions characterized dogs' rates of facial expressivity with more accuracy for dogs with plainer faces. Especially relevant to interspecies communication and cooperation, within-subject analyses revealed that dogs' muscle movements were distributed more evenly across their facial regions in a highly social test condition compared to conditions in which they received ambiguous cues from their owners. On the whole, this study provides an original evaluation of how facial features may impact communication in human-dog interactions.