A Thestral is a breed of winged horses with a skeletal body, face with reptilian features, and wide, leathery wings that resemble a bat's. They are very rare, and are considered dangerous by the Ministry of Magic.
A dog collar is a piece of material put around the neck of a dog. A collar may be used for control, identification, fashion, or other purposes. Identification tags and medical information are often placed on dog collars. Collars are also useful for controlling a dog manually, as they provide a handle for grabbing.
These negative traits are not Dachshund traits, they are small dog syndrome traits. Meaning, most owners treat their small dogs like babies, rather than giving them leadership, As well as rules they need to follow along with limits they are, and are not allowed to do, which all dogs instinctually crave.