A few days ago American media spread laconic news about “a research student rescued - from a tree which she climbed on - by a state Department of Natural Resources helicopter crew, after coming across wolves northeast of Winthrop, Washington, a popular recreation area”. Most probably those wolves lied/snoozed/did something neutral, while the mentioned person - on the tree above them - was feeling “surrounded”.
It is really hard to believe in the wolf pack surrounding and patiently waiting for the preyed animal to be reachable (i.e. trapped on a tree), when their biological hunt strategy is based on prey drive (predatory sequence). Ambush-and-pursuit behavior belongs to feline - canine competitive - predators (vide genus Panthera, genus Lynx, wild/domestic cat) which hunt their prey using claws on their paws instead of grabbing and biting it. They do it solo (except lions), not working collectively like a wolf pack does. Wolves are also used to wandering around their territory (wolf pack, scent marking) and/or migrating to another one (singular wolf), making their standard distance several dozen kilometers (after food) or several hundreds (searching for a partner for life).
Trail up the south side of Tiffany Mountain in the Okanogan Wenatchee National Forest, Okanogan County, Washington, USA /photo credit: Jsayre64/
The majority of animal behavior is instinctive, based on instinct - genetically conditioned hereditary ability of animals (including humans) to proceed according to specific behavioral sequences driven by impulses and controlled by selected external stimulus, being primary conditions for survival of an individual and in consequence - for a population survival.
Three canonical conditions have to be fulfilled to make it happen - safety, food reachability and chance for reproduction (within a species, influencing the entire population).
Considering the crucial meaning of the existential aspect
– singular wolf can attack if it feels endangered/cornered -> direct confrontation, individual decision;
– wolf pack can attack if they’re hungry -> predatory sequence, collective work, instinctive behavior.
Fear is an exemplary elementary emotion, a primal drive associated with self-protection and hazard avoidance. It appears when the life, health or just safety are endangered, affecting a particular individual (directly) or its offspring/partner/mates (indirectly). Every time, it physiologically aims to prepare organism for an immediate escape or for aggressive attack (muscle tension, freezing, hair standing up). Passive defence (camouflage) accompanies the active defence relying on action. Canis lupus species representatives use multiple range of less or more expressive stress signals presented when in danger, ending with warning ones (growling, teeth exhibiting). Their function is to prevent the crossing of the critical distance by a potential intruder - a specified abstract border after which being crossed an animal would attack (because of fear, in defence). A wolf (especially a wild one, not habituated to human presence nearby) chooses escape as a priority (including wolves in sanctuaries and their contact with unfamiliar visitors at the enclosure). Concluding, defensive procedures attend upon interspecific interactions - in wildlife, a human is a hazard for a wolf (escape mechanism trigger) or a competitive predator (habitat competition), depending on conditions. Intraspecific interactions (vide conflicts) are solved mostly by affiliative (submissive postures, calming signals) and antagonistic behavior - related to controlled aggression (if a potential intruder disregards established critical distance). Every confronted animal (also not predatory like a chased herbivore, scared scavenger, preyed rodent) will try to avoid confrontation if it’s possible and fight if it’s confronted. That’s the reason why statistically, approximately 10% of wolf hunts end up successfully. That’s also the reason why wolves in a pack choose an injured/diseased/old or just inexperienced animal for their prey. Scandinavian scientists researched how much distance a human can approach unnoticed to a wild wolf before it would escape. Results gained approximately 106m (17-310 depending on wind strength/direction and if it was a wolf pack or a singular wolf). After that, for an hour, startled ones became distant to circa 1,2km away from the critical place. Relying on wildlife photographers reports, who managed to find a wolf den during the sensitive period of mating season - April (an offspring is born) - August (an offspring is relatively unassisted) - even when camera operator is extremely close to it, a wild leading wolf pair does not attack an intruder, choosing to walk away supported by warning signals, and observe from a safe distance.
Obtaining food is necessary to stay alive. Wolves are predators, their diet is strictly carnivorous. Wolf pack, in accordance with its natural instinct, hunts collectively, remaining prepared for a failure possibility, trying to feed themselves fully if it succeeds (irregularity is associated with their physiology). Collective work, cooperation and sharing-a-prey ability, are obligatory if large ungulates are preyed animals. Individually or in a group, wolves chase their prey estimating own state and capabilities in terms of habitat (too fast prey, injured/diseased/old or inexperienced predator). That’s the reason why statistically, approximately 10% of wolf hunts end up successfully (Yes, again). From an ethological perspective, instinct is determined by behavioral sequences which are constant - each one consists the preceding phase typical for preparative behavior, and succeeding one within limits of executive action (consumption). In this context, Canis lupus prey drive is a specific behavior sequence inherited by generations, initiated and proceeded as a hunt strategy.
SEARCHING -> TRACKING -> STALKING -> CHASING -> GRABBING -> KILLING -> DISSECTING -> EATING
It means that typical gray wolf can kill and consume its prey, wherein a movement is significant - chased animal is a trigger for prey drive, its escape is a hunt strategy element.
Attack of Wolves, Alfred Wierusz-Kowalski (1890), oil on canvas
Speculating about a hypothetical, provocative situation (forgetting for a while that wolves are nocturnal hunters) - an injured/tired/nervous human would have to get lost in the deep forest, hit on a lone hungry inexperienced wolf (or a young wolf being away from its pack), freeze and thereon start to run, screaming in panic, gesticulating and stumbling on roots/entangling into shrubbery.
Well, being honest, it would be hard to resist even for a domestic dog, Canis lupus subspecies. Trained guard dog’s behavior (triggered on command or not) and natural fetch/retrieval, all of them were shaped on the primal canine predatory sequence as well as the following a moving object/person in move.
If the rest of a hypothetical wolf pack would be informed (howling), the hunt strategy could be triggered and proceeded.. until it would turned out that the preyed animal is a human, without other food resources nearby. In prehistoric, ancient or typical for medieval Eurasia times, starving wolves collectively stalked - then chased - humans in vast wild areas (vide Siberia), doing it because of their food resources, like horses, sled dogs or reindeer herded from one place to another. For example: every creation of Polish painter Alfred Wierusz-Kowalski (at the turn of 19th/20th century), impacted by his childhood wolf-attack-on-horse-drawn cart experience depicted a wolf pack chasing a horse-drawn cart to attack horses
(or wolves just behaving neutrally somewhere in their natural habitat).
Being strict - the gray wolf does not like human meat and smell (perspiration, breath, pulse/heart rate), which excludes a hunt strategy proceeding by usage of subsequent chains of predatory sequence (like searching, tracking or stalking), containing whole or partial wolf pack. Wolf diet is composed of herbivores - generally ungulates, optionally rodents and hares/rabbits; sporadically mesopredatory foxes. Coyotes or free-ranging dogs are most of all killed when they intrude a wolf pack territory. Inhabited area does matter - it is divided between wolf packs coming from the local population. More vast wolf pack territory, less probability of hitting on its members in the deep forest.
Till this day, in modern Europe, there wasn’t any documented incident caused by a pure, wild, healthy wolf. Majority of reported occurrences were/are caused by rabid ones, hybrids (dog-wolf crossed grown up offspring) or just wolf-like dogs mistaken with a wolf. Early 1900s, in Canada, James Watson Curran set a reward (some sum of money) to anyone who will prove that indeed a wolf attacked a human. Set reward has waited for 25 years and the real incident didn’t happen (within the local area). Amount of money collected year by year in case of his reward, were destined for wolf science researchers future works. Official list of wolf attacks on humans does not exist, where every incident was scientifically confirmed according to strict rules like it happens in case of predation on livestock - predominantly DNA analysis is obligatory as an evidence.
Final question remain - What kind of research/study was mentioned “research student” doing walking around “a popular recreation area”: Prior to the incident, the individual observed wolf tracks and heard yipping and barking for a period of time before the wolves approached. After unsuccessful attempts to scare the wolves away (including yelling, waving and deploying a can of bear spray in the direction of the wolves) the individual climbed a tree and used a radio to call for assistance. A Loup Loup pack den site is in the vicinity of the site where the incident occurred, and GPS collar data from the early morning of July 12 shows at least one adult wolf from the Loup Loup pack in close proximity to the area where the incident occurred. US Fish and Wildlife Service (USFWS) and Washington Department of Fish and Wildlife (WDFW) biologists believe the location is a “rendezvous” site, and the wolves were likely acting in a defensive manner to protect offspring or food sources. Rendezvous sites are home or activity sites where weaned pups are brought from the den until they are old enough to join adult wolves in hunting activity. - via USFWS (Washington, July 13th, 2018).
 paraphrased after The Associated Press (OKANOGAN, WA (AP); Jul 13th, 2018)
 Reproduction is a process, inherent for living beings, concerning mating male and female individuals within the same species in purpose of an offspring (short-term) and to provide globally a species survival within a local population (long-term). Parents pass part of their genome to their children (fifty-fifty from both of them) taking care for their offspring in accordance with a caring instinct - providing a safety, development and nutrition. In nature, environment is limited, that’s why internal mechanism of population stands for natural selection, in pursuance of which stronger, healthier, more adaptive individuals get a chance to survive (youngsters), afterwards leading as a result to pass genome in further process (adults). In turn, the migration between ecosystems (environments) - reasoned also by looking for another food resources - stands for the reassurance of genetic diversity.
 It makes a human different from omnivore brown bear - food resources competitor (in the shared habitat).
 At what distance do wolves move away from an approaching human (2007), at the Department of Ecology, Swedish University of Agricultural Sciences, research by J. Karlsson, M. Eriksson, O. Liberga.
 Gray Wolf Conservation and Management - Washington Department of Fish and Wildlife
“Canadian Folk: Portraits of Remarkable Lives”, Peter Unwin (2013).
“The fear of wolves: A review of wolf attacks on humans”, (NINA) Norwegian Institute for Nature Research (2002).