user13901: I love most aspects of Buddhism but I can't agree that animals have a "lower" rebirth than us. Dogs for example sometimes have enormous love and compassion for their owners, even if they are being terribly mistreated. I am a vegan because I love animals; animals do not harm us, yet humans routinely kill animals for their own sensual pleasure. The dairy and egg industries are also very cruel -- all those male chickens being killed! And how female dairy cows are always kept pregnant or lactating through artificially insemination. It's human cruelty that keeps them in their difficult position. Saying "It's just their bad karma" is in my opinion a way of weakening your own karma.  
Many animals are somewhat psychic -- they sense things that humans can't. Personally I would rather come back as an animal than a human. They seem more peaceful, humans are constantly thinking and doing and stressing about things. So can I still be a Buddhist, with these beliefs? 

user13904: Regarding the original question... the behavior of animals is in most cases conditioned.
An animal might behave peaceful because its body, its genetics, its upbringing essentially shape it that way, which is just another way of forcing, you could even call it total, absolute forcing since if someone beats you until you behave, at least you can perceive that, you can perceive that it did not come from you; for animals, they're forced in ways they cannot even perceive, but the result is there.
The goal is to attain conscious, intentional, and with understanding good behavior, not a forced one. And that you can only do in a human form.
The forced good behavior is a forced lesson, for those who were too stubborn to learn in any other way. But it is just a part of their path; by itself, forced good behavior can only show to that individual some possibilities, but ultimately it must again be brought to the stage where it can understand and make a conscious, informed decision about how it is going to behave.

user-1: In addition to all the other answers I would like to add the point missed. It is that, you cannot attain Nibbana in the animal realm. It is only in human form where the conditions are right in terms of suffering and ability to learn dhamma, that you can attain Nibbana. So in that sense animals are 'lower' than us.
So, even if you wish for birth in animal realm, you will some day end up being a human, again and again you must practise dhamma to liberate yourself.
Also, don't confuse animal welfare with being a mis-anthrop.

user471: According to SN 56.36 (quoted below), the planes of misery (including the animal realm) are so great and vast. Only a human being who has right view and understands the Four Noble Truth would escape it.

“Bhikkhus, suppose a man were to cut up whatever grass, sticks,
  branches, and foliage there is in this Jambudipa and collect them into
  a single heap. Having done so, he would impale the large creatures in
  the ocean on the large stakes, the middle-sized creatures on the
  middle-sized stakes, and the small creatures on the small stakes.
  Still, bhikkhus, the gross creatures in the ocean would not be
  exhausted even after all the grass, sticks, branches, and foliage in
  Jambudipa had been used up and exhausted. The small creatures in the
  ocean that could not easily be impaled on stakes would be even more
  numerous than this. For what reason? Because of the minuteness of
  their bodies.
“So vast, bhikkhus, is the plane of misery. The person who is
  accomplished in view, freed from that vast plane of misery,
  understands as it really is: ‘This is suffering.’… ‘This is the way
  leading to the cessation of suffering.’
“Therefore, bhikkhus, an exertion should be made to understand: ‘This
  is suffering.’… An exertion should be made to understand: ‘This is the
  way leading to the cessation of suffering.’”

According to SN 56.48, a human birth is very rare and precious, and being able to listen to the Dhamma is also rare. Hence, it is our duty to contemplate on the Four Noble Truths.
The story from the commentary to Dhammapada 338-343 is also useful to illustrate that even good situations don't last forever:

On one occasion, while the Buddha was on an alms-round at Rajagaha, he
  saw a young dirty sow and smiled. When asked by the Venerable Ananda,
  the Buddha replied, "Ananda, this young sow was a hen during the time
  of Kakusandha Buddha. As she was then staying near a refectory in a
  monastery she used to hear the recitation of the sacred text and the
  discourses on the Dhamma. When she died she was reborn as a princess.
  On one occasion, while going to the latrine, the princess noticed the
  maggots and she became mindful of the loathsomeness of the body, etc.
  When she died she was reborn in the Brahma realm as a puthujjana
  brahma but later due to some evil kamma, she was reborn as a sow.
  Ananda! Look, on account of good and evil kamma there is no end of the
  round of existences."


user2282: 
Personally I would rather come back as an animal than a human. They seem more peaceful, humans are constantly thinking and doing and stressing about things.

Be very careful what you wish for. You forgot the fact that the nice peaceful life of those animals you're familiar with are only for the few domesticated pets while the overwhelming majority of animals in the wild or the jungle live a life of constant fear and ignorance. If you were an animal in the wild, chances are pretty good that you'd be eaten alive by another bigger animal up higher in the food chain. True, some humans are very cruel, but at least there're still written rules to protect basic human right. There's no right in the animal world. There's only one rule, the jungle rule.

user13375: Lower is not meant as a moral judgement nor a pejorative in this case. It is meant simply as a statement of the more dire predicament most animals are in compared to most humans. There certainly exist individual dogs, cats, horses, pigs, donkeys, monkeys, deer, sheep, cows, chickens, fish, birds, reptiles that are more compassionate and exhibit virtues superior to individual humans in this very life. However, generally speaking humans have a greater capacity for understanding dharma and opportunity to practice. Most animals are subject to base instinct and spend the vast majority of their time just trying to survive. In this sense it is called the lower or less fortunate realms.

user254: So can I still be a Buddhist, with these beliefs?
Yes of course.
Maybe don't over-idealise animals though, e.g. a real dog might chase and kill grass-hoppers or mice or anything else unless you stop it, fight with other dogs and so on unless it's properly trained.
So I think a human, who is kind and self-restrained and so on, is more admirable.
Instead of coming back as an animal, why not come back as a Buddhist then?
Apart from that, maybe you're doing three things:

Comparing humans to animals, and saying that humans shouldn't compare themselves favourably. That (i.e. "comparing") reminds me of this topic about pride -- and the famous "Does a dog have Buddha-nature?" koan.
Expressing an admiration or at least a sympathy towards animals
Expressing some antipathy, aversion, towards "human cruelty"

Humans seem to be predators/carnivores. What I know of ecology suggests that animal life is unfortunate even without humans in the equation: with animal predators, starvation, no medicine, unable to hear or understand the dharma, and so on -- and there's maybe only quite a limited extent to which we as a single human can fix that. But maybe, being vegan, you are doing what you can -- a proper emotion isn't hatred (towards human or animal predators) but gratitude or joy and so on (that you and other people are able to learn and conduct yourself better).

Incidentally, if you didn't know, being vegan is a point of controversy. Some Buddhists say it's important, other Buddhists say "I'm not killing animals I'm only buying dead meat at the market".
So much so that you get suggestions like, "All the vegetarian questions should get herded into a single thread", i.e. it's a fairly endless debate, difficult to say what hasn't been said before, and difficult to change another person's opinions on the subject.

13901: <p>I love most aspects of Buddhism but I can't agree that animals have a "lower" rebirth than us. Dogs for example sometimes have enormous love and compassion for their owners, even if they are being terribly mistreated. I am a vegan because I love animals; animals do not harm us, yet humans routinely kill animals for their own sensual pleasure. The dairy and egg industries are also very cruel -- all those male chickens being killed! And how female dairy cows are always kept pregnant or lactating through artificially insemination. It's human cruelty that keeps them in their difficult position. Saying "It's just their bad karma" is in my opinion a way of weakening your own karma.  </p>

<p>Many animals are somewhat psychic -- they sense things that humans can't. Personally I would rather come back as an animal than a human. They seem more peaceful, humans are constantly thinking and doing and stressing about things. So can I still be a Buddhist, with these beliefs? </p>
 13904: <p>Regarding the original question... the behavior of animals is in most cases <strong>conditioned</strong>.
An animal might behave peaceful because its body, its genetics, its upbringing essentially shape it that way, which is just another way of forcing, you could even call it total, absolute forcing since if someone beats you until you behave, at least you can perceive that, you can perceive that it did not come from you; for animals, they're forced in ways they cannot even perceive, but the result is there.</p>

<p>The goal is to attain <strong>conscious, intentional, and with understanding</strong> good behavior, not a forced one. And that you can only do in a human form.</p>

<p>The forced good behavior is a forced lesson, for those who were too stubborn to learn in any other way. But it is just a part of their path; by itself, forced good behavior can only show to that individual some possibilities, but ultimately it must again be brought to the stage where it can understand and make a conscious, informed decision about how it is going to behave.</p>
 -1: <p>In addition to all the other answers I would like to add the point missed. It is that, you cannot attain Nibbana in the animal realm. It is only in human form where the conditions are right in terms of suffering and ability to learn dhamma, that you can attain Nibbana. So in that sense animals are 'lower' than us.</p>

<p>So, even if you wish for birth in animal realm, you will some day end up being a human, again and again you must practise dhamma to liberate yourself.</p>

<p>Also, don't confuse animal welfare with being a mis-anthrop.</p>
 471: <p>According to <a href="https://suttacentral.net/sn56.36/en/bodhi" rel="nofollow noreferrer">SN 56.36</a> (quoted below), the planes of misery (including the animal realm) are so great and vast. Only a human being who has right view and understands the Four Noble Truth would escape it.</p>

<blockquote>
  <p>“Bhikkhus, suppose a man were to cut up whatever grass, sticks,
  branches, and foliage there is in this Jambudipa and collect them into
  a single heap. Having done so, he would impale the large creatures in
  the ocean on the large stakes, the middle-sized creatures on the
  middle-sized stakes, and the small creatures on the small stakes.
  Still, bhikkhus, the gross creatures in the ocean would not be
  exhausted even after all the grass, sticks, branches, and foliage in
  Jambudipa had been used up and exhausted. The small creatures in the
  ocean that could not easily be impaled on stakes would be even more
  numerous than this. For what reason? Because of the minuteness of
  their bodies.</p>
  
  <p>“So vast, bhikkhus, is the plane of misery. The person who is
  accomplished in view, freed from that vast plane of misery,
  understands as it really is: ‘This is suffering.’… ‘This is the way
  leading to the cessation of suffering.’</p>
  
  <p>“Therefore, bhikkhus, an exertion should be made to understand: ‘This
  is suffering.’… An exertion should be made to understand: ‘This is the
  way leading to the cessation of suffering.’”</p>
</blockquote>

<p>According to <a href="https://www.accesstoinsight.org/tipitaka/sn/sn56/sn56.048.than.html" rel="nofollow noreferrer">SN 56.48</a>, a human birth is very rare and precious, and being able to listen to the Dhamma is also rare. Hence, it is our duty to contemplate on the Four Noble Truths.</p>

<p>The story from the commentary to <a href="http://www.tipitaka.net/tipitaka/dhp/verseload.php?verse=338" rel="nofollow noreferrer">Dhammapada 338-343</a> is also useful to illustrate that even good situations don't last forever:</p>

<blockquote>
  <p>On one occasion, while the Buddha was on an alms-round at Rajagaha, he
  saw a young dirty sow and smiled. When asked by the Venerable Ananda,
  the Buddha replied, "Ananda, this young sow was a hen during the time
  of Kakusandha Buddha. As she was then staying near a refectory in a
  monastery she used to hear the recitation of the sacred text and the
  discourses on the Dhamma. When she died she was reborn as a princess.
  On one occasion, while going to the latrine, the princess noticed the
  maggots and she became mindful of the loathsomeness of the body, etc.
  When she died she was reborn in the Brahma realm as a puthujjana
  brahma but later due to some evil kamma, she was reborn as a sow.
  Ananda! Look, on account of good and evil kamma there is no end of the
  round of existences."</p>
</blockquote>
 2282: <blockquote>
  <p>Personally I would rather come back as an animal than a human. They seem more peaceful, humans are constantly thinking and doing and stressing about things.</p>
</blockquote>

<p>Be very careful what you wish for. You forgot the fact that the nice peaceful life of those animals you're familiar with are only for the few domesticated pets while the overwhelming majority of animals in the wild or the jungle live a life of constant fear and ignorance. If you were an animal in the wild, chances are pretty good that you'd be eaten alive by another bigger animal up higher in the food chain. True, some humans are very cruel, but at least there're still written rules to protect basic human right. There's no right in the animal world. There's only one rule, the jungle rule.</p>
 13375: <p>Lower is not meant as a moral judgement nor a pejorative in this case. It is meant simply as a statement of the more dire predicament most animals are in compared to most humans. There certainly exist individual dogs, cats, horses, pigs, donkeys, monkeys, deer, sheep, cows, chickens, fish, birds, reptiles that are more compassionate and exhibit virtues superior to individual humans in this very life. However, <em>generally</em> speaking humans have a greater capacity for <em>understanding</em> dharma and opportunity to practice. Most animals are subject to base instinct and spend the vast majority of their time just trying to survive. In this sense it is called the lower or less fortunate realms.</p>
 254: <p><strong>So can I still be a Buddhist, with these beliefs?</strong></p>

<p>Yes of course.</p>

<p>Maybe don't over-idealise animals though, e.g. a real dog might chase and kill grass-hoppers or mice or anything else unless you stop it, fight with other dogs and so on unless it's properly trained.</p>

<p>So I think a human, who is kind and self-restrained and so on, is more admirable.</p>

<p>Instead of coming back as an animal, why not come back as a Buddhist then?</p>

<p>Apart from that, maybe you're doing three things:</p>

<ul>
<li>Comparing humans to animals, and saying that humans shouldn't compare themselves favourably. That (i.e. "comparing") reminds me of <a href="https://buddhism.stackexchange.com/q/9415/254">this topic</a> about pride -- and the famous "Does a dog have Buddha-nature?" koan.</li>
<li>Expressing an admiration or at least a sympathy towards animals</li>
<li>Expressing some antipathy, aversion, towards "human cruelty"</li>
</ul>

<p>Humans seem to be predators/carnivores. What I know of ecology suggests that animal life is unfortunate even without humans in the equation: with animal predators, starvation, no medicine, unable to hear or understand the dharma, and so on -- and there's maybe only quite a limited extent to which we as a single human can fix that. But maybe, being vegan, you are doing what you can -- a proper emotion isn't hatred (towards human or animal predators) but gratitude or joy and so on (that you and other people are able to learn and conduct yourself better).</p>

<hr>

<p>Incidentally, if you didn't know, being vegan is a point of controversy. Some Buddhists say it's important, other Buddhists say "I'm not killing animals I'm only buying dead meat at the market".</p>

<p>So much so that you get <a href="https://buddhism.meta.stackexchange.com/a/116/254">suggestions like</a>, "All the vegetarian questions should get herded into a single thread", i.e. it's a fairly endless debate, difficult to say what hasn't been said before, and difficult to change another person's opinions on the subject.</p>
